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	$40.27	13.349%	$45.6456	$45.65	$45.65	$45.60
Purchase #2	$129.67	5.549%	$136.8654	$136.87	$136.85	$136.90
Purchase #3	$90.74	4.597%	$94.9113	$94.91	$94.90	$94.90
Purchase #4	$177.29	6.778%	$189.3067	$189.31	$189.30	$189.30
Purchase #5	$250.89	7.396%	$269.4458	$269.45	$269.45	$269.40
Purchase #6	$242.41	13.494%	$275.1208	$275.12	$275.10	$275.10
Purchase #7	$65.92	13.230%	$74.6412	$74.64	$74.65	$74.60
7 purchase totals =	$997.19		$1,085.9368	$1,085.95	$1,085.90	$1,085.80