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 $41.27   13.465%   $46.827   $46.83   $46.85   $46.80  
  Purchase #2 $235.60   10.378%   $260.0506   $260.05   $260.05   $260.10  
  Purchase #3 $10.43   4.610%   $10.9108   $10.91   $10.90   $10.90  
  Purchase #4 $138.68   7.826%   $149.5331   $149.53   $149.55   $149.50  
  Purchase #5 $110.45   6.133%   $117.2239   $117.22   $117.20   $117.20  
  Purchase #6 $86.95   11.732%   $97.151   $97.15   $97.15   $97.20  
  Purchase #7 $39.91   12.253%   $44.8002   $44.80   $44.80   $44.80  
  7 purchase totals = $663.29       $726.4966   $726.49   $726.50   $726.50