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	$203.77	9.472%	$223.0711	$223.07	$223.05	$223.10
Purchase #2	$32.31	3.469%	$33.4308	$33.43	$33.45	$33.40
Purchase #3	$153.78	12.313%	$172.7149	$172.71	$172.70	$172.70
Purchase #4	$83.33	7.271%	$89.3889	$89.39	$89.40	$89.40
Purchase #5	$229.78	11.675%	$256.6068	$256.61	$256.60	$256.60
Purchase #6	$16.56	6.679%	$17.666	$17.67	$17.65	$17.70
Purchase #7	$130.33	7.758%	$140.441	$140.44	$140.45	$140.40
7 purchase totals =	$849.86		$933.3195	$933.32	$933.30	$933.30