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 $66.90   13.254%   $75.7669   $75.77   $75.75   $75.80  
  Purchase #2 $207.32   8.138%   $224.1917   $224.19   $224.20   $224.20  
  Purchase #3 $37.31   10.655%   $41.2854   $41.29   $41.30   $41.30  
  Purchase #4 $198.84   10.783%   $220.2809   $220.28   $220.30   $220.30  
  Purchase #5 $59.80   9.625%   $65.5558   $65.56   $65.55   $65.60  
  Purchase #6 $171.66   10.269%   $189.2878   $189.29   $189.30   $189.30  
  Purchase #7 $190.33   13.315%   $215.6724   $215.67   $215.65   $215.70  
  7 purchase totals = $932.16       $1,032.0409   $1,032.05   $1,032.05   $1,032.20