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 $214.61   9.414%   $234.8134   $234.81   $234.80   $234.80  
  Purchase #2 $245.79   9.152%   $268.2847   $268.28   $268.30   $268.30  
  Purchase #3 $163.32   11.625%   $182.306   $182.31   $182.30   $182.30  
  Purchase #4 $84.79   10.670%   $93.8371   $93.84   $93.85   $93.80  
  Purchase #5 $55.38   8.393%   $60.028   $60.03   $60.05   $60.00  
  Purchase #6 $189.49   11.166%   $210.6485   $210.65   $210.65   $210.60  
  Purchase #7 $41.56   9.511%   $45.5128   $45.51   $45.50   $45.50  
  7 purchase totals = $994.94       $1,095.4305   $1,095.43   $1,095.45   $1,095.30