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	$170.74	11.780%	$190.8532	$190.85	$190.85	$190.90
Purchase #2	$158.76	3.641%	$164.5405	$164.54	$164.55	$164.50
Purchase #3	$143.64	4.290%	$149.8022	$149.80	$149.80	$149.80
Purchase #4	$168.51	4.308%	$175.7694	$175.77	$175.75	$175.80
Purchase #5	$230.57	7.528%	$247.9273	$247.93	$247.95	$247.90
Purchase #6	$127.73	10.483%	$141.1199	$141.12	$141.10	$141.10
Purchase #7	$216.49	6.376%	$230.2934	$230.29	$230.30	$230.30
7 purchase totals =	$1,216.44		$1,300.3059	$1,300.30	$1,300.30	$1,300.30