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	$224.65	11.337%	$250.1186	$250.12	$250.10	$250.10
Purchase #2	$223.42	6.754%	$238.5098	$238.51	$238.50	$238.50
Purchase #3	$241.32	11.690%	$269.5303	$269.53	$269.55	$269.50
Purchase #4	$247.75	6.325%	$263.4202	$263.42	$263.40	$263.40
Purchase #5	$194.36	7.624%	$209.178	$209.18	$209.20	$209.20
Purchase #6	$78.86	6.160%	$83.7178	$83.72	$83.70	$83.70
Purchase #7	$245.56	10.724%	$271.8939	$271.89	$271.90	$271.90
7 purchase totals =	$1,455.92		$1,586.3686	$1,586.37	$1,586.35	$1,586.30