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 $84.46   13.140%   $95.558   $95.56   $95.55   $95.60  
  Purchase #2 $100.60   8.744%   $109.3965   $109.40   $109.40   $109.40  
  Purchase #3 $90.57   11.402%   $100.8968   $100.90   $100.90   $100.90  
  Purchase #4 $9.26   7.440%   $9.9489   $9.95   $9.95   $9.90  
  Purchase #5 $205.61   3.867%   $213.5609   $213.56   $213.55   $213.60  
  Purchase #6 $191.87   3.793%   $199.1476   $199.15   $199.15   $199.10  
  Purchase #7 $234.32   4.112%   $243.9552   $243.96   $243.95   $244.00  
  7 purchase totals = $916.69       $972.4639   $972.48   $972.45   $972.50