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 $241.69   8.531%   $262.3086   $262.31   $262.30   $262.30  
  Purchase #2 $132.29   8.849%   $143.9963   $144.00   $144.00   $144.00  
  Purchase #3 $147.72   13.741%   $168.0182   $168.02   $168.00   $168.00  
  Purchase #4 $181.35   9.103%   $197.8583   $197.86   $197.85   $197.90  
  Purchase #5 $139.30   6.851%   $148.8434   $148.84   $148.85   $148.80  
  Purchase #6 $178.95   4.485%   $186.9759   $186.98   $187.00   $187.00  
  Purchase #7 $10.68   3.314%   $11.0339   $11.03   $11.05   $11.00  
  7 purchase totals = $1,031.98       $1,119.0346   $1,119.04   $1,119.05   $1,119.00