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 $82.59   13.784%   $93.9742   $93.97   $93.95   $94.00  
  Purchase #2 $200.60   7.146%   $214.9349   $214.93   $214.95   $214.90  
  Purchase #3 $85.92   12.608%   $96.7528   $96.75   $96.75   $96.80  
  Purchase #4 $126.25   12.717%   $142.3052   $142.31   $142.30   $142.30  
  Purchase #5 $136.61   4.133%   $142.2561   $142.26   $142.25   $142.30  
  Purchase #6 $209.43   9.741%   $229.8306   $229.83   $229.85   $229.80  
  Purchase #7 $192.88   7.790%   $207.9054   $207.91   $207.90   $207.90  
  7 purchase totals = $1,034.28       $1,127.9592   $1,127.96   $1,127.95   $1,128.00