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	$158.61	8.763%	$172.509	$172.51	$172.50	$172.50
Purchase #2	$106.26	3.481%	$109.9589	$109.96	$109.95	$110.00
Purchase #3	$98.57	12.873%	$111.2589	$111.26	$111.25	$111.30
Purchase #4	$63.65	13.290%	$72.1091	$72.11	$72.10	$72.10
Purchase #5	$22.55	10.433%	$24.9026	$24.90	$24.90	$24.90
Purchase #6	$93.97	4.547%	$98.2428	$98.24	$98.25	$98.20
Purchase #7	$17.41	11.604%	$19.4303	$19.43	$19.45	$19.40
7 purchase totals =	$561.02		$608.4116	$608.41	$608.40	$608.40