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 $87.59   8.511%   $95.0448   $95.04   $95.05   $95.00  
  Purchase #2 $241.69   13.507%   $274.3351   $274.34   $274.35   $274.30  
  Purchase #3 $55.70   6.452%   $59.2938   $59.29   $59.30   $59.30  
  Purchase #4 $135.54   11.799%   $151.5324   $151.53   $151.55   $151.50  
  Purchase #5 $166.59   6.288%   $177.0652   $177.07   $177.05   $177.10  
  Purchase #6 $81.36   5.306%   $85.677   $85.68   $85.70   $85.70  
  Purchase #7 $201.42   9.637%   $220.8308   $220.83   $220.85   $220.80  
  7 purchase totals = $969.89       $1,063.7791   $1,063.78   $1,063.85   $1,063.70