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 $68.57   8.435%   $74.3539   $74.35   $74.35   $74.40  
  Purchase #2 $138.41   9.303%   $151.2863   $151.29   $151.30   $151.30  
  Purchase #3 $207.35   10.642%   $229.4162   $229.42   $229.40   $229.40  
  Purchase #4 $82.94   10.280%   $91.4662   $91.47   $91.45   $91.50  
  Purchase #5 $158.41   7.682%   $170.5791   $170.58   $170.60   $170.60  
  Purchase #6 $135.85   13.191%   $153.77   $153.77   $153.75   $153.80  
  Purchase #7 $164.50   6.708%   $175.5347   $175.53   $175.55   $175.50  
  7 purchase totals = $956.03       $1,046.4064   $1,046.41   $1,046.40   $1,046.50