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 $46.98   4.193%   $48.9499   $48.95   $48.95   $48.90  
  Purchase #2 $147.67   4.118%   $153.7511   $153.75   $153.75   $153.80  
  Purchase #3 $69.79   9.379%   $76.3356   $76.34   $76.35   $76.30  
  Purchase #4 $161.47   13.378%   $183.0715   $183.07   $183.05   $183.10  
  Purchase #5 $244.71   6.395%   $260.3592   $260.36   $260.35   $260.40  
  Purchase #6 $169.48   9.778%   $186.0518   $186.05   $186.05   $186.10  
  Purchase #7 $151.30   10.168%   $166.6842   $166.68   $166.70   $166.70  
  7 purchase totals = $991.40       $1,075.2033   $1,075.20   $1,075.20   $1,075.30