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	$172.55	6.191%	$183.2326	$183.23	$183.25	$183.20
Purchase #2	$248.74	6.486%	$264.8733	$264.87	$264.85	$264.90
Purchase #3	$30.25	7.538%	$32.5302	$32.53	$32.55	$32.50
Purchase #4	$226.64	13.358%	$256.9146	$256.91	$256.90	$256.90
Purchase #5	$28.72	11.288%	$31.9619	$31.96	$31.95	$32.00
Purchase #6	$149.87	10.831%	$166.1024	$166.10	$166.10	$166.10
Purchase #7	$186.88	11.571%	$208.5039	$208.50	$208.50	$208.50
7 purchase totals =	$1,043.65		$1,144.1189	$1,144.10	$1,144.10	$1,144.10