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	$157.66	10.290%	$173.8832	$173.88	$173.90	$173.90
Purchase #2	$212.92	11.842%	$238.134	$238.13	$238.15	$238.10
Purchase #3	$33.71	11.311%	$37.5229	$37.52	$37.50	$37.50
Purchase #4	$76.50	12.628%	$86.1604	$86.16	$86.15	$86.20
Purchase #5	$74.59	3.595%	$77.2715	$77.27	$77.25	$77.30
Purchase #6	$137.87	12.692%	$155.3685	$155.37	$155.35	$155.40
Purchase #7	$229.77	6.438%	$244.5626	$244.56	$244.55	$244.60
7 purchase totals =	$923.02		$1,012.9031	$1,012.89	$1,012.85	$1,013.00