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	$98.32	6.245%	$104.4601	$104.46	$104.45	$104.50
Purchase #2	$28.35	3.287%	$29.2819	$29.28	$29.30	$29.30
Purchase #3	$91.33	13.584%	$103.7363	$103.74	$103.75	$103.70
Purchase #4	$28.38	8.229%	$30.7154	$30.72	$30.70	$30.70
Purchase #5	$144.25	7.613%	$155.2318	$155.23	$155.25	$155.20
Purchase #6	$222.78	3.645%	$230.9003	$230.90	$230.90	$230.90
Purchase #7	$93.81	6.830%	$100.2172	$100.22	$100.20	$100.20
7 purchase totals =	$707.22		$754.5430	$754.55	$754.55	$754.50