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	$182.65	5.712%	$193.083	$193.08	$193.10	$193.10
Purchase #2	$241.86	10.112%	$266.3169	$266.32	$266.30	$266.30
Purchase #3	$141.27	9.554%	$154.7669	$154.77	$154.75	$154.80
Purchase #4	$241.31	9.765%	$264.8739	$264.87	$264.85	$264.90
Purchase #5	$148.37	5.281%	$156.2054	$156.21	$156.20	$156.20
Purchase #6	$101.75	9.786%	$111.7073	$111.71	$111.70	$111.70
Purchase #7	$22.60	11.390%	$25.1741	$25.17	$25.15	$25.20
7 purchase totals =	$1,079.81		$1,172.1275	$1,172.13	$1,172.05	$1,172.20