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	$56.36	8.737%	$61.2842	$61.28	$61.30	$61.30
Purchase #2	$163.78	6.233%	$173.9884	$173.99	$174.00	$174.00
Purchase #3	$35.90	4.298%	$37.443	$37.44	$37.45	$37.40
Purchase #4	$113.77	8.155%	$123.0479	$123.05	$123.05	$123.00
Purchase #5	$39.83	9.311%	$43.5386	$43.54	$43.55	$43.50
Purchase #6	$231.52	3.186%	$238.8962	$238.90	$238.90	$238.90
Purchase #7	$13.51	11.329%	$15.0405	$15.04	$15.05	$15.00
7 purchase totals =	$654.67		$693.2388	$693.24	$693.30	$693.10