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 $240.56   9.430%   $263.2448   $263.24   $263.25   $263.20  
  Purchase #2 $84.84   7.261%   $91.0002   $91.00   $91.00   $91.00  
  Purchase #3 $11.37   8.689%   $12.3579   $12.36   $12.35   $12.40  
  Purchase #4 $159.69   5.175%   $167.954   $167.95   $167.95   $168.00  
  Purchase #5 $156.83   8.337%   $169.9049   $169.90   $169.90   $169.90  
  Purchase #6 $230.89   4.308%   $240.8367   $240.84   $240.85   $240.80  
  Purchase #7 $141.67   5.794%   $149.8784   $149.88   $149.90   $149.90  
  7 purchase totals = $1,025.85       $1,095.1769   $1,095.17   $1,095.20   $1,095.20