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	$32.79	7.411%	$35.2201	$35.22	$35.20	$35.20
Purchase #2	$46.36	10.160%	$51.0702	$51.07	$51.05	$51.10
Purchase #3	$40.65	7.362%	$43.6427	$43.64	$43.65	$43.60
Purchase #4	$91.35	3.667%	$94.6998	$94.70	$94.70	$94.70
Purchase #5	$105.58	11.251%	$117.4588	$117.46	$117.45	$117.50
Purchase #6	$89.56	5.444%	$94.4356	$94.44	$94.45	$94.40
Purchase #7	$31.43	6.241%	$33.3915	$33.39	$33.40	$33.40
7 purchase totals =	$437.72		$469.9187	$469.92	$469.90	$469.90