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 $174.26   4.821%   $182.6611   $182.66   $182.65   $182.70  
  Purchase #2 $23.56   6.111%   $24.9998   $25.00   $25.00   $25.00  
  Purchase #3 $177.54   10.119%   $195.5053   $195.51   $195.50   $195.50  
  Purchase #4 $159.53   4.282%   $166.3611   $166.36   $166.35   $166.40  
  Purchase #5 $180.27   13.335%   $204.309   $204.31   $204.30   $204.30  
  Purchase #6 $214.84   9.198%   $234.601   $234.60   $234.60   $234.60  
  Purchase #7 $118.83   11.553%   $132.5584   $132.56   $132.55   $132.60  
  7 purchase totals = $1,048.83       $1,140.9957   $1,141.00   $1,140.95   $1,141.10