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 $101.97   12.414%   $114.6286   $114.63   $114.65   $114.60  
  Purchase #2 $199.63   11.813%   $223.2123   $223.21   $223.20   $223.20  
  Purchase #3 $206.53   11.362%   $229.9959   $230.00   $230.00   $230.00  
  Purchase #4 $104.33   10.477%   $115.2607   $115.26   $115.25   $115.30  
  Purchase #5 $147.76   8.661%   $160.5575   $160.56   $160.55   $160.60  
  Purchase #6 $74.84   11.334%   $83.3224   $83.32   $83.30   $83.30  
  Purchase #7 $118.60   6.536%   $126.3517   $126.35   $126.35   $126.40  
  7 purchase totals = $953.66       $1,053.3291   $1,053.33   $1,053.30   $1,053.40