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 $198.81   8.657%   $216.021   $216.02   $216.00   $216.00  
  Purchase #2 $206.90   9.852%   $227.2838   $227.28   $227.30   $227.30  
  Purchase #3 $101.54   3.246%   $104.836   $104.84   $104.85   $104.80  
  Purchase #4 $105.82   6.236%   $112.4189   $112.42   $112.40   $112.40  
  Purchase #5 $15.95   11.187%   $17.7343   $17.73   $17.75   $17.70  
  Purchase #6 $61.94   4.428%   $64.6827   $64.68   $64.70   $64.70  
  Purchase #7 $233.79   7.585%   $251.523   $251.52   $251.50   $251.50  
  7 purchase totals = $924.75       $994.4997   $994.49   $994.50   $994.40