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	$35.94	7.578%	$38.6635	$38.66	$38.65	$38.70
Purchase #2	$9.82	10.114%	$10.8132	$10.81	$10.80	$10.80
Purchase #3	$47.82	9.848%	$52.5293	$52.53	$52.55	$52.50
Purchase #4	$106.91	4.276%	$111.4815	$111.48	$111.50	$111.50
Purchase #5	$224.88	11.472%	$250.6782	$250.68	$250.70	$250.70
Purchase #6	$78.91	8.431%	$85.5629	$85.56	$85.55	$85.60
Purchase #7	$173.29	4.456%	$181.0118	$181.01	$181.00	$181.00
7 purchase totals =	$677.57		$730.7404	$730.73	$730.75	$730.80