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 $64.36   4.355%   $67.1629   $67.16   $67.15   $67.20  
  Purchase #2 $179.65   8.722%   $195.3191   $195.32   $195.30   $195.30  
  Purchase #3 $223.38   9.465%   $244.5229   $244.52   $244.50   $244.50  
  Purchase #4 $10.56   6.325%   $11.2279   $11.23   $11.25   $11.20  
  Purchase #5 $195.76   3.818%   $203.2341   $203.23   $203.25   $203.20  
  Purchase #6 $101.53   5.250%   $106.8603   $106.86   $106.85   $106.90  
  Purchase #7 $128.85   4.121%   $134.1599   $134.16   $134.15   $134.20  
  7 purchase totals = $904.09       $962.4871   $962.48   $962.45   $962.50