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	$141.48	4.244%	$147.4844	$147.48	$147.50	$147.50
Purchase #2	$66.41	12.131%	$74.4662	$74.47	$74.45	$74.50
Purchase #3	$203.87	3.452%	$210.9076	$210.91	$210.90	$210.90
Purchase #4	$97.93	13.307%	$110.9615	$110.96	$110.95	$111.00
Purchase #5	$103.31	11.253%	$114.9355	$114.94	$114.95	$114.90
Purchase #6	$59.31	10.175%	$65.3448	$65.34	$65.35	$65.30
Purchase #7	$167.50	3.140%	$172.7595	$172.76	$172.75	$172.80
7 purchase totals =	$839.81		$896.8595	$896.86	$896.85	$896.90