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 $145.73   5.604%   $153.8967   $153.90   $153.90   $153.90  
  Purchase #2 $60.79   8.751%   $66.1097   $66.11   $66.10   $66.10  
  Purchase #3 $230.92   4.586%   $241.51   $241.51   $241.50   $241.50  
  Purchase #4 $59.91   5.623%   $63.2787   $63.28   $63.30   $63.30  
  Purchase #5 $100.44   11.489%   $111.9796   $111.98   $112.00   $112.00  
  Purchase #6 $101.41   9.381%   $110.9233   $110.92   $110.90   $110.90  
  Purchase #7 $182.63   12.558%   $205.5647   $205.56   $205.55   $205.60  
  7 purchase totals = $881.83       $953.2627   $953.26   $953.25   $953.30