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 $84.86   10.762%   $93.9926   $93.99   $94.00   $94.00  
  Purchase #2 $169.82   9.205%   $185.4519   $185.45   $185.45   $185.50  
  Purchase #3 $23.81   5.846%   $25.2019   $25.20   $25.20   $25.20  
  Purchase #4 $147.36   11.129%   $163.7597   $163.76   $163.75   $163.80  
  Purchase #5 $119.79   5.690%   $126.6061   $126.61   $126.60   $126.60  
  Purchase #6 $100.48   9.303%   $109.8277   $109.83   $109.85   $109.80  
  Purchase #7 $229.90   3.184%   $237.22   $237.22   $237.20   $237.20  
  7 purchase totals = $876.02       $942.0599   $942.06   $942.05   $942.10