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	$236.57	6.162%	$251.1474	$251.15	$251.15	$251.10
Purchase #2	$231.54	3.171%	$238.8821	$238.88	$238.90	$238.90
Purchase #3	$33.79	13.340%	$38.2976	$38.30	$38.30	$38.30
Purchase #4	$154.33	11.530%	$172.1242	$172.12	$172.10	$172.10
Purchase #5	$64.56	10.493%	$71.3343	$71.33	$71.35	$71.30
Purchase #6	$240.66	8.770%	$261.7659	$261.77	$261.75	$261.80
Purchase #7	$120.74	9.807%	$132.581	$132.58	$132.60	$132.60
7 purchase totals =	$1,082.19		$1,166.1325	$1,166.13	$1,166.15	$1,166.10