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 $194.95   3.783%   $202.325   $202.33   $202.35   $202.30  
  Purchase #2 $194.34   7.546%   $209.0049   $209.00   $209.00   $209.00  
  Purchase #3 $189.81   10.238%   $209.2427   $209.24   $209.25   $209.20  
  Purchase #4 $55.88   7.601%   $60.1274   $60.13   $60.15   $60.10  
  Purchase #5 $95.29   13.334%   $107.996   $108.00   $108.00   $108.00  
  Purchase #6 $161.93   10.301%   $178.6104   $178.61   $178.60   $178.60  
  Purchase #7 $226.29   5.282%   $238.2426   $238.24   $238.25   $238.20  
  7 purchase totals = $1,118.49       $1,205.5490   $1,205.55   $1,205.60   $1,205.40