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	$77.90	12.828%	$87.893	$87.89	$87.90	$87.90
Purchase #2	$182.98	7.461%	$196.6321	$196.63	$196.65	$196.60
Purchase #3	$151.43	9.217%	$165.3873	$165.39	$165.40	$165.40
Purchase #4	$106.33	11.674%	$118.743	$118.74	$118.75	$118.70
Purchase #5	$152.47	4.504%	$159.3372	$159.34	$159.35	$159.30
Purchase #6	$235.70	3.637%	$244.2724	$244.27	$244.25	$244.30
Purchase #7	$180.61	8.842%	$196.5795	$196.58	$196.60	$196.60
7 purchase totals =	$1,087.42		$1,168.8445	$1,168.84	$1,168.90	$1,168.80