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 $62.75   7.288%   $67.3232   $67.32   $67.30   $67.30  
  Purchase #2 $211.39   8.352%   $229.0453   $229.05   $229.05   $229.00  
  Purchase #3 $206.51   12.533%   $232.3919   $232.39   $232.40   $232.40  
  Purchase #4 $67.86   7.868%   $73.1992   $73.20   $73.20   $73.20  
  Purchase #5 $187.45   8.639%   $203.6438   $203.64   $203.65   $203.60  
  Purchase #6 $180.84   10.730%   $200.2441   $200.24   $200.25   $200.20  
  Purchase #7 $209.84   9.353%   $229.4663   $229.47   $229.45   $229.50  
  7 purchase totals = $1,126.64       $1,235.3138   $1,235.31   $1,235.30   $1,235.20