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 $67.84   5.153%   $71.3358   $71.34   $71.35   $71.30  
  Purchase #2 $196.85   6.605%   $209.8519   $209.85   $209.85   $209.90  
  Purchase #3 $20.74   10.733%   $22.966   $22.97   $22.95   $23.00  
  Purchase #4 $100.25   8.503%   $108.7743   $108.77   $108.75   $108.80  
  Purchase #5 $161.46   13.322%   $182.9697   $182.97   $182.95   $183.00  
  Purchase #6 $212.65   13.437%   $241.2238   $241.22   $241.20   $241.20  
  Purchase #7 $118.93   6.109%   $126.1954   $126.20   $126.20   $126.20  
  7 purchase totals = $878.72       $963.3169   $963.32   $963.25   $963.40