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 $41.71   4.846%   $43.7313   $43.73   $43.75   $43.70  
  Purchase #2 $195.92   8.767%   $213.0963   $213.10   $213.10   $213.10  
  Purchase #3 $219.52   9.790%   $241.011   $241.01   $241.00   $241.00  
  Purchase #4 $205.73   12.684%   $231.8248   $231.82   $231.80   $231.80  
  Purchase #5 $82.34   3.112%   $84.9024   $84.90   $84.90   $84.90  
  Purchase #6 $246.84   10.222%   $272.072   $272.07   $272.05   $272.10  
  Purchase #7 $15.50   5.808%   $16.4002   $16.40   $16.40   $16.40  
  7 purchase totals = $1,007.56       $1,103.0380   $1,103.03   $1,103.00   $1,103.00