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	$159.83	7.715%	$172.1609	$172.16	$172.15	$172.20
Purchase #2	$71.60	10.251%	$78.9397	$78.94	$78.95	$78.90
Purchase #3	$54.92	7.816%	$59.2125	$59.21	$59.20	$59.20
Purchase #4	$66.40	3.773%	$68.9053	$68.91	$68.90	$68.90
Purchase #5	$118.46	13.203%	$134.1003	$134.10	$134.10	$134.10
Purchase #6	$58.63	5.497%	$61.8529	$61.85	$61.85	$61.90
Purchase #7	$67.77	12.474%	$76.2236	$76.22	$76.20	$76.20
7 purchase totals =	$597.61		$651.3952	$651.39	$651.35	$651.40