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 $63.34   11.138%   $70.3948   $70.39   $70.40   $70.40  
  Purchase #2 $121.83   9.175%   $133.0079   $133.01   $133.00   $133.00  
  Purchase #3 $79.96   12.702%   $90.1165   $90.12   $90.10   $90.10  
  Purchase #4 $96.44   5.316%   $101.5668   $101.57   $101.55   $101.60  
  Purchase #5 $214.85   8.485%   $233.08   $233.08   $233.10   $233.10  
  Purchase #6 $205.29   7.357%   $220.3932   $220.39   $220.40   $220.40  
  Purchase #7 $95.91   11.110%   $106.5656   $106.57   $106.55   $106.60  
  7 purchase totals = $877.62       $955.1248   $955.13   $955.10   $955.20