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 $58.97   5.200%   $62.0364   $62.04   $62.05   $62.00  
  Purchase #2 $16.53   7.603%   $17.7868   $17.79   $17.80   $17.80  
  Purchase #3 $144.97   4.208%   $151.0703   $151.07   $151.05   $151.10  
  Purchase #4 $34.58   4.444%   $36.1167   $36.12   $36.10   $36.10  
  Purchase #5 $194.27   9.661%   $213.0384   $213.04   $213.05   $213.00  
  Purchase #6 $128.38   9.527%   $140.6108   $140.61   $140.60   $140.60  
  Purchase #7 $68.93   7.646%   $74.2004   $74.20   $74.20   $74.20  
  7 purchase totals = $646.63       $694.8598   $694.87   $694.85   $694.80