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 $92.75   3.130%   $95.6531   $95.65   $95.65   $95.70  
  Purchase #2 $6.85   3.123%   $7.0639   $7.06   $7.05   $7.10  
  Purchase #3 $158.82   11.130%   $176.4967   $176.50   $176.50   $176.50  
  Purchase #4 $203.94   12.407%   $229.2428   $229.24   $229.25   $229.20  
  Purchase #5 $34.91   4.191%   $36.3731   $36.37   $36.35   $36.40  
  Purchase #6 $153.42   11.235%   $170.6567   $170.66   $170.65   $170.70  
  Purchase #7 $216.29   3.858%   $224.6345   $224.63   $224.65   $224.60  
  7 purchase totals = $866.98       $940.1208   $940.11   $940.10   $940.20