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 $65.73   13.865%   $74.8435   $74.84   $74.85   $74.80  
  Purchase #2 $216.75   11.847%   $242.4284   $242.43   $242.45   $242.40  
  Purchase #3 $230.74   6.659%   $246.105   $246.11   $246.10   $246.10  
  Purchase #4 $211.96   12.173%   $237.7619   $237.76   $237.75   $237.80  
  Purchase #5 $118.77   12.374%   $133.4666   $133.47   $133.45   $133.50  
  Purchase #6 $88.51   9.582%   $96.991   $96.99   $97.00   $97.00  
  Purchase #7 $62.69   5.387%   $66.0671   $66.07   $66.05   $66.10  
  7 purchase totals = $995.15       $1,097.6635   $1,097.67   $1,097.65   $1,097.70