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 $175.26   11.149%   $194.7997   $194.80   $194.80   $194.80  
  Purchase #2 $209.93   7.416%   $225.4984   $225.50   $225.50   $225.50  
  Purchase #3 $217.56   5.691%   $229.9413   $229.94   $229.95   $229.90  
  Purchase #4 $126.26   13.540%   $143.3556   $143.36   $143.35   $143.40  
  Purchase #5 $70.62   5.748%   $74.6792   $74.68   $74.70   $74.70  
  Purchase #6 $206.34   8.740%   $224.3741   $224.37   $224.35   $224.40  
  Purchase #7 $200.95   6.349%   $213.7083   $213.71   $213.70   $213.70  
  7 purchase totals = $1,206.92       $1,306.3566   $1,306.36   $1,306.35   $1,306.40