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	$50.74	8.717%	$55.163	$55.16	$55.15	$55.20
Purchase #2	$21.33	13.304%	$24.1677	$24.17	$24.15	$24.20
Purchase #3	$141.97	7.142%	$152.1095	$152.11	$152.10	$152.10
Purchase #4	$107.27	3.784%	$111.3291	$111.33	$111.35	$111.30
Purchase #5	$128.59	11.304%	$143.1258	$143.13	$143.15	$143.10
Purchase #6	$129.88	11.405%	$144.6928	$144.69	$144.70	$144.70
Purchase #7	$104.99	7.317%	$112.6721	$112.67	$112.65	$112.70
7 purchase totals =	$684.77		$743.2600	$743.26	$743.25	$743.30