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 $35.52   5.130%   $37.3422   $37.34   $37.35   $37.30  
  Purchase #2 $170.65   4.675%   $178.6279   $178.63   $178.65   $178.60  
  Purchase #3 $175.92   4.696%   $184.1812   $184.18   $184.20   $184.20  
  Purchase #4 $208.63   11.151%   $231.8943   $231.89   $231.90   $231.90  
  Purchase #5 $51.50   3.303%   $53.201   $53.20   $53.20   $53.20  
  Purchase #6 $137.45   11.557%   $153.3351   $153.34   $153.35   $153.30  
  Purchase #7 $199.40   3.837%   $207.051   $207.05   $207.05   $207.10  
  7 purchase totals = $979.07       $1,045.6327   $1,045.63   $1,045.70   $1,045.60