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	$162.74	12.642%	$183.3136	$183.31	$183.30	$183.30
Purchase #2	$40.92	13.627%	$46.4962	$46.50	$46.50	$46.50
Purchase #3	$240.83	5.767%	$254.7187	$254.72	$254.70	$254.70
Purchase #4	$186.26	4.481%	$194.6063	$194.61	$194.60	$194.60
Purchase #5	$154.62	7.278%	$165.8732	$165.87	$165.85	$165.90
Purchase #6	$223.54	3.687%	$231.7819	$231.78	$231.80	$231.80
Purchase #7	$33.36	3.283%	$34.4552	$34.46	$34.45	$34.50
7 purchase totals =	$1,042.27		$1,111.2451	$1,111.25	$1,111.20	$1,111.30