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 $85.95   11.210%   $95.585   $95.59   $95.60   $95.60  
  Purchase #2 $203.31   9.151%   $221.9149   $221.91   $221.90   $221.90  
  Purchase #3 $32.54   7.322%   $34.9226   $34.92   $34.90   $34.90  
  Purchase #4 $177.97   11.863%   $199.0826   $199.08   $199.10   $199.10  
  Purchase #5 $80.74   8.501%   $87.6037   $87.60   $87.60   $87.60  
  Purchase #6 $117.99   3.761%   $122.4276   $122.43   $122.45   $122.40  
  Purchase #7 $85.63   7.778%   $92.2903   $92.29   $92.30   $92.30  
  7 purchase totals = $784.13       $853.8267   $853.82   $853.85   $853.80