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 $217.47   7.581%   $233.9564   $233.96   $233.95   $234.00  
  Purchase #2 $75.96   5.434%   $80.0877   $80.09   $80.10   $80.10  
  Purchase #3 $165.35   9.462%   $180.9954   $181.00   $181.00   $181.00  
  Purchase #4 $61.78   4.549%   $64.5904   $64.59   $64.60   $64.60  
  Purchase #5 $205.64   10.664%   $227.5694   $227.57   $227.55   $227.60  
  Purchase #6 $44.83   11.441%   $49.959   $49.96   $49.95   $50.00  
  Purchase #7 $195.41   4.446%   $204.0979   $204.10   $204.10   $204.10  
  7 purchase totals = $966.44       $1,041.2562   $1,041.27   $1,041.25   $1,041.40