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 $95.75   6.205%   $101.6913   $101.69   $101.70   $101.70  
  Purchase #2 $198.29   11.252%   $220.6016   $220.60   $220.60   $220.60  
  Purchase #3 $23.38   4.568%   $24.448   $24.45   $24.45   $24.40  
  Purchase #4 $188.72   3.487%   $195.3007   $195.30   $195.30   $195.30  
  Purchase #5 $49.84   8.317%   $53.9852   $53.99   $54.00   $54.00  
  Purchase #6 $24.43   5.811%   $25.8496   $25.85   $25.85   $25.80  
  Purchase #7 $217.54   3.591%   $225.3519   $225.35   $225.35   $225.40  
  7 purchase totals = $797.95       $847.2283   $847.23   $847.25   $847.20