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 $32.48   11.425%   $36.1908   $36.19   $36.20   $36.20  
  Purchase #2 $245.77   9.707%   $269.6269   $269.63   $269.65   $269.60  
  Purchase #3 $33.37   10.323%   $36.8148   $36.81   $36.80   $36.80  
  Purchase #4 $231.86   3.266%   $239.4325   $239.43   $239.45   $239.40  
  Purchase #5 $79.67   5.852%   $84.3323   $84.33   $84.35   $84.30  
  Purchase #6 $238.92   11.321%   $265.9681   $265.97   $265.95   $266.00  
  Purchase #7 $166.57   8.276%   $180.3553   $180.36   $180.35   $180.40  
  7 purchase totals = $1,028.64       $1,112.7207   $1,112.72   $1,112.75   $1,112.70