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	$161.50	12.184%	$181.1772	$181.18	$181.20	$181.20
Purchase #2	$112.64	12.776%	$127.0309	$127.03	$127.05	$127.00
Purchase #3	$230.74	3.675%	$239.2197	$239.22	$239.20	$239.20
Purchase #4	$93.82	6.252%	$99.6856	$99.69	$99.70	$99.70
Purchase #5	$210.98	8.348%	$228.5926	$228.59	$228.60	$228.60
Purchase #6	$98.67	12.835%	$111.3343	$111.33	$111.35	$111.30
Purchase #7	$147.70	7.849%	$159.293	$159.29	$159.30	$159.30
7 purchase totals =	$1,056.05		$1,146.3333	$1,146.33	$1,146.40	$1,146.30