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	$187.53	4.874%	$196.6702	$196.67	$196.65	$196.70
Purchase #2	$241.95	9.222%	$264.2626	$264.26	$264.25	$264.30
Purchase #3	$247.89	9.496%	$271.4296	$271.43	$271.45	$271.40
Purchase #4	$172.33	10.830%	$190.9933	$190.99	$191.00	$191.00
Purchase #5	$99.95	13.329%	$113.2723	$113.27	$113.25	$113.30
Purchase #6	$16.52	10.318%	$18.2245	$18.22	$18.20	$18.20
Purchase #7	$60.97	13.395%	$69.1369	$69.14	$69.15	$69.10
7 purchase totals =	$1,027.14		$1,123.9894	$1,123.98	$1,123.95	$1,124.00