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	$214.50	13.406%	$243.2559	$243.26	$243.25	$243.30
Purchase #2	$52.65	5.621%	$55.6095	$55.61	$55.60	$55.60
Purchase #3	$116.87	12.342%	$131.2941	$131.29	$131.30	$131.30
Purchase #4	$122.57	4.716%	$128.3504	$128.35	$128.35	$128.40
Purchase #5	$118.70	12.672%	$133.7417	$133.74	$133.75	$133.70
Purchase #6	$222.67	3.109%	$229.5928	$229.59	$229.60	$229.60
Purchase #7	$137.25	10.789%	$152.0579	$152.06	$152.05	$152.10
7 purchase totals =	$985.21		$1,073.9023	$1,073.90	$1,073.90	$1,074.00