Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $196.73   5.715%   $207.9731   $207.97   $207.95   $208.00  
  Purchase #2 $173.83   11.682%   $194.1368   $194.14   $194.15   $194.10  
  Purchase #3 $203.54   3.852%   $211.3804   $211.38   $211.40   $211.40  
  Purchase #4 $235.96   6.855%   $252.1351   $252.14   $252.15   $252.10  
  Purchase #5 $134.68   5.308%   $141.8288   $141.83   $141.85   $141.80  
  Purchase #6 $103.84   3.857%   $107.8451   $107.85   $107.85   $107.80  
  Purchase #7 $142.82   5.710%   $150.975   $150.98   $151.00   $151.00  
  7 purchase totals = $1,191.40       $1,266.2743   $1,266.29   $1,266.35   $1,266.20