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 $68.37   8.180%   $73.9627   $73.96   $73.95   $74.00  
  Purchase #2 $189.39   11.753%   $211.649   $211.65   $211.65   $211.60  
  Purchase #3 $54.76   10.207%   $60.3494   $60.35   $60.35   $60.30  
  Purchase #4 $162.51   7.828%   $175.2313   $175.23   $175.25   $175.20  
  Purchase #5 $85.94   7.438%   $92.3322   $92.33   $92.35   $92.30  
  Purchase #6 $47.34   12.873%   $53.4341   $53.43   $53.45   $53.40  
  Purchase #7 $187.78   8.117%   $203.0221   $203.02   $203.00   $203.00  
  7 purchase totals = $796.09       $869.9808   $869.97   $870.00   $869.80