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 $114.74   9.782%   $125.9639   $125.96   $125.95   $126.00  
  Purchase #2 $201.51   4.538%   $210.6545   $210.65   $210.65   $210.70  
  Purchase #3 $95.41   11.239%   $106.1331   $106.13   $106.15   $106.10  
  Purchase #4 $42.67   6.539%   $45.4602   $45.46   $45.45   $45.50  
  Purchase #5 $105.39   12.264%   $118.315   $118.32   $118.30   $118.30  
  Purchase #6 $101.98   10.758%   $112.951   $112.95   $112.95   $113.00  
  Purchase #7 $133.59   13.702%   $151.8945   $151.89   $151.90   $151.90  
  7 purchase totals = $795.29       $871.3722   $871.36   $871.35   $871.50