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 $87.32   12.756%   $98.4585   $98.46   $98.45   $98.50  
  Purchase #2 $225.50   9.421%   $246.7444   $246.74   $246.75   $246.70  
  Purchase #3 $44.52   9.845%   $48.903   $48.90   $48.90   $48.90  
  Purchase #4 $107.40   10.323%   $118.4869   $118.49   $118.50   $118.50  
  Purchase #5 $199.44   13.139%   $225.6444   $225.64   $225.65   $225.60  
  Purchase #6 $185.34   9.553%   $203.0455   $203.05   $203.05   $203.00  
  Purchase #7 $237.27   7.255%   $254.4839   $254.48   $254.50   $254.50  
  7 purchase totals = $1,086.79       $1,195.7666   $1,195.76   $1,195.80   $1,195.70