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 $93.64   4.606%   $97.9531   $97.95   $97.95   $98.00  
  Purchase #2 $244.34   10.274%   $269.4435   $269.44   $269.45   $269.40  
  Purchase #3 $32.32   3.830%   $33.5579   $33.56   $33.55   $33.60  
  Purchase #4 $194.49   10.689%   $215.279   $215.28   $215.30   $215.30  
  Purchase #5 $161.33   11.752%   $180.2895   $180.29   $180.30   $180.30  
  Purchase #6 $6.26   11.165%   $6.9589   $6.96   $6.95   $7.00  
  Purchase #7 $203.76   5.744%   $215.464   $215.46   $215.45   $215.50  
  7 purchase totals = $936.14       $1,018.9459   $1,018.94   $1,018.95   $1,019.10