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	$43.84	6.106%	$46.5169	$46.52	$46.50	$46.50
Purchase #2	$94.64	7.538%	$101.774	$101.77	$101.75	$101.80
Purchase #3	$100.56	10.529%	$111.148	$111.15	$111.15	$111.10
Purchase #4	$65.43	4.591%	$68.4339	$68.43	$68.45	$68.40
Purchase #5	$133.67	7.184%	$143.2729	$143.27	$143.25	$143.30
Purchase #6	$32.64	6.802%	$34.8602	$34.86	$34.85	$34.90
Purchase #7	$220.74	13.200%	$249.8777	$249.88	$249.90	$249.90
7 purchase totals =	$691.52		$755.8836	$755.88	$755.85	$755.90