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 $116.98   7.314%   $125.5359   $125.54   $125.55   $125.50  
  Purchase #2 $207.95   4.143%   $216.5654   $216.57   $216.55   $216.60  
  Purchase #3 $150.26   11.374%   $167.3506   $167.35   $167.35   $167.40  
  Purchase #4 $112.96   3.194%   $116.5679   $116.57   $116.55   $116.60  
  Purchase #5 $80.52   3.709%   $83.5065   $83.51   $83.50   $83.50  
  Purchase #6 $111.61   12.261%   $125.2945   $125.29   $125.30   $125.30  
  Purchase #7 $166.95   6.197%   $177.2959   $177.30   $177.30   $177.30  
  7 purchase totals = $947.23       $1,012.1167   $1,012.13   $1,012.10   $1,012.20