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 $160.69   4.401%   $167.762   $167.76   $167.75   $167.80  
  Purchase #2 $58.91   5.845%   $62.3533   $62.35   $62.35   $62.40  
  Purchase #3 $232.45   9.662%   $254.9093   $254.91   $254.90   $254.90  
  Purchase #4 $77.75   6.400%   $82.726   $82.73   $82.75   $82.70  
  Purchase #5 $184.39   8.242%   $199.5874   $199.59   $199.60   $199.60  
  Purchase #6 $107.44   13.305%   $121.7349   $121.73   $121.75   $121.70  
  Purchase #7 $204.42   5.250%   $215.1521   $215.15   $215.15   $215.20  
  7 purchase totals = $1,026.05       $1,104.2250   $1,104.22   $1,104.25   $1,104.30