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 $162.76   8.108%   $175.9566   $175.96   $175.95   $176.00  
  Purchase #2 $148.62   12.813%   $167.6627   $167.66   $167.65   $167.70  
  Purchase #3 $105.43   6.506%   $112.2893   $112.29   $112.30   $112.30  
  Purchase #4 $221.60   3.261%   $228.8264   $228.83   $228.85   $228.80  
  Purchase #5 $143.34   11.379%   $159.6507   $159.65   $159.65   $159.70  
  Purchase #6 $60.89   4.233%   $63.4675   $63.47   $63.45   $63.50  
  Purchase #7 $140.71   8.802%   $153.0953   $153.10   $153.10   $153.10  
  7 purchase totals = $983.35       $1,060.9485   $1,060.96   $1,060.95   $1,061.10