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	$235.79	8.824%	$256.5961	$256.60	$256.60	$256.60
Purchase #2	$228.50	6.307%	$242.9115	$242.91	$242.90	$242.90
Purchase #3	$51.31	5.613%	$54.19	$54.19	$54.20	$54.20
Purchase #4	$158.37	13.250%	$179.354	$179.35	$179.35	$179.40
Purchase #5	$22.30	13.228%	$25.2498	$25.25	$25.25	$25.20
Purchase #6	$216.73	7.577%	$233.1516	$233.15	$233.15	$233.20
Purchase #7	$31.54	10.702%	$34.9154	$34.92	$34.90	$34.90
7 purchase totals =	$944.54		$1,026.3684	$1,026.37	$1,026.35	$1,026.40