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 $70.38   3.464%   $72.818   $72.82   $72.80   $72.80  
  Purchase #2 $51.49   12.559%   $57.9566   $57.96   $57.95   $58.00  
  Purchase #3 $189.66   6.553%   $202.0884   $202.09   $202.10   $202.10  
  Purchase #4 $157.72   3.364%   $163.0257   $163.03   $163.05   $163.00  
  Purchase #5 $169.81   9.838%   $186.5159   $186.52   $186.50   $186.50  
  Purchase #6 $221.71   4.769%   $232.2833   $232.28   $232.30   $232.30  
  Purchase #7 $243.41   4.192%   $253.6137   $253.61   $253.60   $253.60  
  7 purchase totals = $1,104.18       $1,168.3016   $1,168.31   $1,168.30   $1,168.30