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 $183.75   5.725%   $194.2697   $194.27   $194.25   $194.30  
  Purchase #2 $75.28   3.232%   $77.713   $77.71   $77.70   $77.70  
  Purchase #3 $140.35   10.633%   $155.2734   $155.27   $155.25   $155.30  
  Purchase #4 $245.70   8.694%   $267.0612   $267.06   $267.05   $267.10  
  Purchase #5 $122.60   11.309%   $136.4648   $136.46   $136.45   $136.50  
  Purchase #6 $131.97   13.634%   $149.9628   $149.96   $149.95   $150.00  
  Purchase #7 $181.73   10.455%   $200.7299   $200.73   $200.75   $200.70  
  7 purchase totals = $1,081.38       $1,181.4748   $1,181.46   $1,181.40   $1,181.60