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	$148.64	8.111%	$160.6962	$160.70	$160.70	$160.70
Purchase #2	$46.78	11.295%	$52.0638	$52.06	$52.05	$52.10
Purchase #3	$47.46	7.278%	$50.9141	$50.91	$50.90	$50.90
Purchase #4	$205.50	13.388%	$233.0123	$233.01	$233.00	$233.00
Purchase #5	$165.32	12.208%	$185.5023	$185.50	$185.50	$185.50
Purchase #6	$211.33	6.727%	$225.5462	$225.55	$225.55	$225.50
Purchase #7	$159.89	3.726%	$165.8475	$165.85	$165.85	$165.80
7 purchase totals =	$984.92		$1,073.5824	$1,073.58	$1,073.55	$1,073.50