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	$111.61	5.123%	$117.3278	$117.33	$117.35	$117.30
Purchase #2	$39.60	13.752%	$45.0458	$45.05	$45.05	$45.00
Purchase #3	$54.31	4.315%	$56.6535	$56.65	$56.65	$56.70
Purchase #4	$91.60	8.841%	$99.6984	$99.70	$99.70	$99.70
Purchase #5	$146.90	13.763%	$167.1178	$167.12	$167.10	$167.10
Purchase #6	$91.83	13.412%	$104.1462	$104.15	$104.15	$104.10
Purchase #7	$40.67	3.606%	$42.1366	$42.14	$42.15	$42.10
7 purchase totals =	$576.52		$632.1261	$632.14	$632.15	$632.00