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	$33.58	10.413%	$37.0767	$37.08	$37.10	$37.10
Purchase #2	$53.71	6.285%	$57.0857	$57.09	$57.10	$57.10
Purchase #3	$56.92	4.667%	$59.5765	$59.58	$59.60	$59.60
Purchase #4	$84.36	12.772%	$95.1345	$95.13	$95.15	$95.10
Purchase #5	$166.37	11.661%	$185.7704	$185.77	$185.75	$185.80
Purchase #6	$101.82	3.747%	$105.6352	$105.64	$105.65	$105.60
Purchase #7	$68.76	12.843%	$77.5908	$77.59	$77.60	$77.60
7 purchase totals =	$565.52		$617.8698	$617.88	$617.95	$617.90