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 $61.45   13.849%   $69.9602   $69.96   $69.95   $70.00  
  Purchase #2 $112.60   6.236%   $119.6217   $119.62   $119.60   $119.60  
  Purchase #3 $207.62   4.176%   $216.2902   $216.29   $216.30   $216.30  
  Purchase #4 $192.66   8.565%   $209.1613   $209.16   $209.15   $209.20  
  Purchase #5 $244.75   3.235%   $252.6677   $252.67   $252.65   $252.70  
  Purchase #6 $181.89   7.188%   $194.9643   $194.96   $194.95   $195.00  
  Purchase #7 $83.36   13.746%   $94.8187   $94.82   $94.80   $94.80  
  7 purchase totals = $1,084.33       $1,157.4841   $1,157.48   $1,157.40   $1,157.60