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 $191.75   6.764%   $204.72   $204.72   $204.70   $204.70  
  Purchase #2 $97.49   4.464%   $101.842   $101.84   $101.85   $101.80  
  Purchase #3 $193.44   4.197%   $201.5587   $201.56   $201.55   $201.60  
  Purchase #4 $40.61   6.415%   $43.2151   $43.22   $43.20   $43.20  
  Purchase #5 $33.74   9.454%   $36.9298   $36.93   $36.95   $36.90  
  Purchase #6 $50.94   8.432%   $55.2353   $55.24   $55.25   $55.20  
  Purchase #7 $133.37   9.569%   $146.1322   $146.13   $146.15   $146.10  
  7 purchase totals = $741.34       $789.6331   $789.64   $789.65   $789.50