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 $11.86   7.341%   $12.7306   $12.73   $12.75   $12.70  
  Purchase #2 $213.96   9.505%   $234.2969   $234.30   $234.30   $234.30  
  Purchase #3 $241.84   9.120%   $263.8958   $263.90   $263.90   $263.90  
  Purchase #4 $104.74   13.391%   $118.7657   $118.77   $118.75   $118.80  
  Purchase #5 $199.75   6.237%   $212.2084   $212.21   $212.20   $212.20  
  Purchase #6 $5.68   4.414%   $5.9307   $5.93   $5.95   $5.90  
  Purchase #7 $206.88   4.288%   $215.751   $215.75   $215.75   $215.80  
  7 purchase totals = $984.71       $1,063.5791   $1,063.59   $1,063.60   $1,063.60