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 $181.94   8.691%   $197.7524   $197.75   $197.75   $197.80  
  Purchase #2 $225.98   8.230%   $244.5782   $244.58   $244.60   $244.60  
  Purchase #3 $127.62   4.145%   $132.9098   $132.91   $132.90   $132.90  
  Purchase #4 $227.86   3.335%   $235.4591   $235.46   $235.45   $235.50  
  Purchase #5 $190.36   13.836%   $216.6982   $216.70   $216.70   $216.70  
  Purchase #6 $165.87   4.123%   $172.7088   $172.71   $172.70   $172.70  
  Purchase #7 $39.86   3.548%   $41.2742   $41.27   $41.25   $41.30  
  7 purchase totals = $1,159.49       $1,241.3807   $1,241.38   $1,241.35   $1,241.50