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 $174.41   10.801%   $193.248   $193.25   $193.25   $193.20  
  Purchase #2 $68.72   9.352%   $75.1467   $75.15   $75.15   $75.10  
  Purchase #3 $216.68   5.385%   $228.3482   $228.35   $228.35   $228.30  
  Purchase #4 $229.69   12.289%   $257.9166   $257.92   $257.90   $257.90  
  Purchase #5 $118.43   13.416%   $134.3186   $134.32   $134.30   $134.30  
  Purchase #6 $92.70   5.215%   $97.5343   $97.53   $97.55   $97.50  
  Purchase #7 $182.79   6.645%   $194.9364   $194.94   $194.95   $194.90  
  7 purchase totals = $1,083.42       $1,181.4488   $1,181.46   $1,181.45   $1,181.20