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	$25.75	7.236%	$27.6133	$27.61	$27.60	$27.60
Purchase #2	$34.51	8.173%	$37.3305	$37.33	$37.35	$37.30
Purchase #3	$37.66	4.259%	$39.2639	$39.26	$39.25	$39.30
Purchase #4	$74.73	9.611%	$81.9123	$81.91	$81.90	$81.90
Purchase #5	$70.49	10.524%	$77.9084	$77.91	$77.90	$77.90
Purchase #6	$11.31	5.121%	$11.8892	$11.89	$11.90	$11.90
Purchase #7	$207.58	7.172%	$222.4676	$222.47	$222.45	$222.50
7 purchase totals =	$462.03		$498.3852	$498.38	$498.35	$498.40