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 $66.91   7.253%   $71.763   $71.76   $71.75   $71.80  
  Purchase #2 $222.41   6.578%   $237.0401   $237.04   $237.05   $237.00  
  Purchase #3 $97.98   11.804%   $109.5456   $109.55   $109.55   $109.50  
  Purchase #4 $143.53   4.303%   $149.7061   $149.71   $149.70   $149.70  
  Purchase #5 $42.31   5.351%   $44.574   $44.57   $44.55   $44.60  
  Purchase #6 $141.65   6.732%   $151.1859   $151.19   $151.20   $151.20  
  Purchase #7 $160.96   10.716%   $178.2085   $178.21   $178.20   $178.20  
  7 purchase totals = $875.75       $942.0232   $942.03   $942.00   $942.00