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	$151.75	5.425%	$159.9824	$159.98	$160.00	$160.00
Purchase #2	$53.95	7.286%	$57.8808	$57.88	$57.90	$57.90
Purchase #3	$18.47	5.790%	$19.5394	$19.54	$19.55	$19.50
Purchase #4	$56.38	11.631%	$62.9376	$62.94	$62.95	$62.90
Purchase #5	$156.78	9.149%	$171.1238	$171.12	$171.10	$171.10
Purchase #6	$36.59	9.743%	$40.155	$40.16	$40.15	$40.20
Purchase #7	$99.64	13.553%	$113.1442	$113.14	$113.15	$113.10
7 purchase totals =	$573.56		$624.7632	$624.76	$624.80	$624.70