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 $89.27   8.245%   $96.6303   $96.63   $96.65   $96.60  
  Purchase #2 $222.91   8.462%   $241.7726   $241.77   $241.75   $241.80  
  Purchase #3 $167.88   9.615%   $184.0217   $184.02   $184.00   $184.00  
  Purchase #4 $112.53   8.347%   $121.9229   $121.92   $121.90   $121.90  
  Purchase #5 $117.65   12.581%   $132.4515   $132.45   $132.45   $132.50  
  Purchase #6 $59.62   9.559%   $65.3191   $65.32   $65.30   $65.30  
  Purchase #7 $210.34   3.325%   $217.3338   $217.33   $217.35   $217.30  
  7 purchase totals = $980.20       $1,059.4519   $1,059.44   $1,059.40   $1,059.40