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 $85.28   12.711%   $96.1199   $96.12   $96.10   $96.10  
  Purchase #2 $131.91   13.198%   $149.3195   $149.32   $149.30   $149.30  
  Purchase #3 $219.92   7.388%   $236.1677   $236.17   $236.15   $236.20  
  Purchase #4 $143.50   4.407%   $149.824   $149.82   $149.80   $149.80  
  Purchase #5 $94.26   5.730%   $99.6611   $99.66   $99.65   $99.70  
  Purchase #6 $94.56   13.153%   $106.9975   $107.00   $107.00   $107.00  
  Purchase #7 $205.69   8.860%   $223.9141   $223.91   $223.90   $223.90  
  7 purchase totals = $975.12       $1,062.0038   $1,062.00   $1,061.90   $1,062.00