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	$243.90	4.499%	$254.8731	$254.87	$254.85	$254.90
Purchase #2	$242.31	9.325%	$264.9054	$264.91	$264.90	$264.90
Purchase #3	$71.39	11.111%	$79.3221	$79.32	$79.30	$79.30
Purchase #4	$48.88	11.828%	$54.6615	$54.66	$54.65	$54.70
Purchase #5	$167.94	5.154%	$176.5956	$176.60	$176.60	$176.60
Purchase #6	$57.83	12.637%	$65.138	$65.14	$65.15	$65.10
Purchase #7	$17.40	9.580%	$19.0669	$19.07	$19.05	$19.10
7 purchase totals =	$849.65		$914.5626	$914.57	$914.50	$914.60