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 $194.52   5.130%   $204.4989   $204.50   $204.50   $204.50  
  Purchase #2 $193.28   4.511%   $201.9989   $202.00   $202.00   $202.00  
  Purchase #3 $51.44   5.592%   $54.3165   $54.32   $54.30   $54.30  
  Purchase #4 $149.98   9.713%   $164.5476   $164.55   $164.55   $164.50  
  Purchase #5 $5.27   11.714%   $5.8873   $5.89   $5.90   $5.90  
  Purchase #6 $238.36   9.642%   $261.3427   $261.34   $261.35   $261.30  
  Purchase #7 $150.61   12.515%   $169.4588   $169.46   $169.45   $169.50  
  7 purchase totals = $983.46       $1,062.0507   $1,062.06   $1,062.05   $1,062.00