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	$182.72	8.509%	$198.2676	$198.27	$198.25	$198.30
Purchase #2	$224.91	8.694%	$244.4637	$244.46	$244.45	$244.50
Purchase #3	$54.88	7.793%	$59.1568	$59.16	$59.15	$59.20
Purchase #4	$71.51	8.223%	$77.3903	$77.39	$77.40	$77.40
Purchase #5	$79.46	11.161%	$88.3285	$88.33	$88.35	$88.30
Purchase #6	$149.92	6.660%	$159.9047	$159.90	$159.90	$159.90
Purchase #7	$42.77	6.472%	$45.5381	$45.54	$45.55	$45.50
7 purchase totals =	$806.17		$873.0497	$873.05	$873.05	$873.10