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 $83.74   10.498%   $92.531   $92.53   $92.55   $92.50  
  Purchase #2 $210.29   12.754%   $237.1104   $237.11   $237.10   $237.10  
  Purchase #3 $61.32   4.638%   $64.164   $64.16   $64.15   $64.20  
  Purchase #4 $157.61   9.647%   $172.8146   $172.81   $172.80   $172.80  
  Purchase #5 $46.69   11.522%   $52.0696   $52.07   $52.05   $52.10  
  Purchase #6 $221.93   8.131%   $239.9751   $239.98   $240.00   $240.00  
  Purchase #7 $181.61   11.335%   $202.1955   $202.20   $202.20   $202.20  
  7 purchase totals = $963.19       $1,060.8602   $1,060.86   $1,060.85   $1,060.90