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 $162.60   8.747%   $176.8226   $176.82   $176.80   $176.80  
  Purchase #2 $244.44   13.462%   $277.3465   $277.35   $277.35   $277.30  
  Purchase #3 $68.38   3.776%   $70.962   $70.96   $70.95   $71.00  
  Purchase #4 $215.73   9.413%   $236.0367   $236.04   $236.05   $236.00  
  Purchase #5 $138.31   8.672%   $150.3042   $150.30   $150.30   $150.30  
  Purchase #6 $175.60   11.343%   $195.5183   $195.52   $195.50   $195.50  
  Purchase #7 $58.34   7.156%   $62.5148   $62.51   $62.50   $62.50  
  7 purchase totals = $1,063.40       $1,169.5051   $1,169.50   $1,169.45   $1,169.40