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 $196.58   4.580%   $205.5834   $205.58   $205.60   $205.60  
  Purchase #2 $132.73   12.784%   $149.6982   $149.70   $149.70   $149.70  
  Purchase #3 $80.37   4.602%   $84.0686   $84.07   $84.05   $84.10  
  Purchase #4 $116.54   7.465%   $125.2397   $125.24   $125.25   $125.20  
  Purchase #5 $98.60   11.572%   $110.01   $110.01   $110.00   $110.00  
  Purchase #6 $237.88   5.222%   $250.3021   $250.30   $250.30   $250.30  
  Purchase #7 $197.49   12.870%   $222.907   $222.91   $222.90   $222.90  
  7 purchase totals = $1,060.19       $1,147.8090   $1,147.81   $1,147.80   $1,147.80