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	$198.70	12.649%	$223.8336	$223.83	$223.85	$223.80
Purchase #2	$193.68	11.636%	$216.2166	$216.22	$216.20	$216.20
Purchase #3	$85.37	4.348%	$89.0819	$89.08	$89.10	$89.10
Purchase #4	$67.32	6.128%	$71.4454	$71.45	$71.45	$71.40
Purchase #5	$98.74	6.782%	$105.4365	$105.44	$105.45	$105.40
Purchase #6	$182.89	5.213%	$192.4241	$192.42	$192.40	$192.40
Purchase #7	$146.91	8.326%	$159.1417	$159.14	$159.15	$159.10
7 purchase totals =	$973.61		$1,057.5798	$1,057.58	$1,057.60	$1,057.40