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	$147.26	8.373%	$159.5901	$159.59	$159.60	$159.60
Purchase #2	$121.72	4.522%	$127.2242	$127.22	$127.20	$127.20
Purchase #3	$99.99	8.751%	$108.7401	$108.74	$108.75	$108.70
Purchase #4	$237.66	7.546%	$255.5938	$255.59	$255.60	$255.60
Purchase #5	$41.70	10.138%	$45.9275	$45.93	$45.95	$45.90
Purchase #6	$138.35	10.834%	$153.3388	$153.34	$153.35	$153.30
Purchase #7	$154.80	3.673%	$160.4858	$160.49	$160.50	$160.50
7 purchase totals =	$941.48		$1,010.9003	$1,010.90	$1,010.95	$1,010.80