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 $117.92   7.196%   $126.4055   $126.41   $126.40   $126.40  
  Purchase #2 $142.74   9.223%   $155.9049   $155.90   $155.90   $155.90  
  Purchase #3 $6.56   7.332%   $7.041   $7.04   $7.05   $7.00  
  Purchase #4 $182.49   5.163%   $191.912   $191.91   $191.90   $191.90  
  Purchase #5 $186.71   9.205%   $203.8967   $203.90   $203.90   $203.90  
  Purchase #6 $48.65   5.677%   $51.4119   $51.41   $51.40   $51.40  
  Purchase #7 $108.75   6.689%   $116.0243   $116.02   $116.00   $116.00  
  7 purchase totals = $793.82       $852.5963   $852.59   $852.55   $852.50