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 $188.79   6.472%   $201.0085   $201.01   $201.00   $201.00  
  Purchase #2 $178.86   13.123%   $202.3318   $202.33   $202.35   $202.30  
  Purchase #3 $95.84   8.525%   $104.0104   $104.01   $104.00   $104.00  
  Purchase #4 $131.59   9.455%   $144.0318   $144.03   $144.05   $144.00  
  Purchase #5 $88.35   6.614%   $94.1935   $94.19   $94.20   $94.20  
  Purchase #6 $183.46   11.239%   $204.0791   $204.08   $204.10   $204.10  
  Purchase #7 $57.98   8.218%   $62.7448   $62.74   $62.75   $62.70  
  7 purchase totals = $924.87       $1,012.3999   $1,012.39   $1,012.45   $1,012.30