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 $186.25   8.376%   $201.8503   $201.85   $201.85   $201.90  
  Purchase #2 $165.96   5.641%   $175.3218   $175.32   $175.30   $175.30  
  Purchase #3 $169.41   10.505%   $187.2065   $187.21   $187.20   $187.20  
  Purchase #4 $85.84   11.122%   $95.3871   $95.39   $95.40   $95.40  
  Purchase #5 $10.37   6.279%   $11.0211   $11.02   $11.00   $11.00  
  Purchase #6 $112.79   11.471%   $125.7281   $125.73   $125.75   $125.70  
  Purchase #7 $233.72   5.251%   $245.9926   $245.99   $246.00   $246.00  
  7 purchase totals = $964.34       $1,042.5075   $1,042.51   $1,042.50   $1,042.50