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 $82.89   11.740%   $92.6213   $92.62   $92.60   $92.60  
  Purchase #2 $96.68   9.429%   $105.796   $105.80   $105.80   $105.80  
  Purchase #3 $131.79   8.735%   $143.3019   $143.30   $143.30   $143.30  
  Purchase #4 $161.74   5.125%   $170.0292   $170.03   $170.05   $170.00  
  Purchase #5 $104.86   11.728%   $117.158   $117.16   $117.15   $117.20  
  Purchase #6 $41.43   10.360%   $45.7221   $45.72   $45.70   $45.70  
  Purchase #7 $233.27   4.753%   $244.3573   $244.36   $244.35   $244.40  
  7 purchase totals = $852.66       $918.9858   $918.99   $918.95   $919.00