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 $54.54   9.448%   $59.6929   $59.69   $59.70   $59.70  
  Purchase #2 $206.78   11.772%   $231.1221   $231.12   $231.10   $231.10  
  Purchase #3 $220.74   8.270%   $238.9952   $239.00   $239.00   $239.00  
  Purchase #4 $133.95   13.340%   $151.8189   $151.82   $151.80   $151.80  
  Purchase #5 $214.85   10.482%   $237.3706   $237.37   $237.35   $237.40  
  Purchase #6 $62.82   8.436%   $68.1195   $68.12   $68.10   $68.10  
  Purchase #7 $202.85   3.535%   $210.0207   $210.02   $210.00   $210.00  
  7 purchase totals = $1,096.53       $1,197.1399   $1,197.14   $1,197.05   $1,197.10