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	$146.86	7.516%	$157.898	$157.90	$157.90	$157.90
Purchase #2	$142.27	10.575%	$157.3151	$157.32	$157.30	$157.30
Purchase #3	$142.56	6.314%	$151.5612	$151.56	$151.55	$151.60
Purchase #4	$102.28	13.810%	$116.4049	$116.40	$116.40	$116.40
Purchase #5	$9.78	8.399%	$10.6014	$10.60	$10.60	$10.60
Purchase #6	$211.55	10.268%	$233.272	$233.27	$233.25	$233.30
Purchase #7	$22.29	8.325%	$24.1456	$24.15	$24.15	$24.10
7 purchase totals =	$777.59		$851.1982	$851.20	$851.15	$851.20