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 $198.68   7.711%   $214.0002   $214.00   $214.00   $214.00  
  Purchase #2 $63.77   4.174%   $66.4318   $66.43   $66.45   $66.40  
  Purchase #3 $90.87   5.215%   $95.6089   $95.61   $95.60   $95.60  
  Purchase #4 $202.75   3.747%   $210.347   $210.35   $210.35   $210.30  
  Purchase #5 $106.26   4.273%   $110.8005   $110.80   $110.80   $110.80  
  Purchase #6 $163.92   3.781%   $170.1178   $170.12   $170.10   $170.10  
  Purchase #7 $224.39   5.189%   $236.0336   $236.03   $236.05   $236.00  
  7 purchase totals = $1,050.64       $1,103.3398   $1,103.34   $1,103.35   $1,103.20