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 $35.70   4.375%   $37.2619   $37.26   $37.25   $37.30  
  Purchase #2 $245.42   6.869%   $262.2779   $262.28   $262.30   $262.30  
  Purchase #3 $193.91   12.626%   $218.3931   $218.39   $218.40   $218.40  
  Purchase #4 $173.97   5.151%   $182.9312   $182.93   $182.95   $182.90  
  Purchase #5 $181.39   7.771%   $195.4858   $195.49   $195.50   $195.50  
  Purchase #6 $37.80   9.242%   $41.2935   $41.29   $41.30   $41.30  
  Purchase #7 $227.66   11.862%   $254.665   $254.67   $254.65   $254.70  
  7 purchase totals = $1,095.85       $1,192.3084   $1,192.31   $1,192.35   $1,192.40