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	$151.91	6.868%	$162.3432	$162.34	$162.35	$162.30
Purchase #2	$195.69	6.595%	$208.5958	$208.60	$208.60	$208.60
Purchase #3	$245.89	10.795%	$272.4338	$272.43	$272.45	$272.40
Purchase #4	$41.80	9.761%	$45.8801	$45.88	$45.90	$45.90
Purchase #5	$154.54	12.116%	$173.2641	$173.26	$173.25	$173.30
Purchase #6	$79.81	10.845%	$88.4654	$88.47	$88.45	$88.50
Purchase #7	$199.37	11.667%	$222.6305	$222.63	$222.65	$222.60
7 purchase totals =	$1,069.01		$1,173.6129	$1,173.61	$1,173.65	$1,173.60