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	$162.33	10.600%	$179.537	$179.54	$179.55	$179.50
Purchase #2	$135.61	3.102%	$139.8166	$139.82	$139.80	$139.80
Purchase #3	$225.41	6.344%	$239.71	$239.71	$239.70	$239.70
Purchase #4	$51.36	11.303%	$57.1652	$57.17	$57.15	$57.20
Purchase #5	$238.32	7.300%	$255.7174	$255.72	$255.70	$255.70
Purchase #6	$155.27	11.129%	$172.55	$172.55	$172.55	$172.60
Purchase #7	$161.83	5.323%	$170.4442	$170.44	$170.45	$170.40
7 purchase totals =	$1,130.13		$1,214.9404	$1,214.95	$1,214.90	$1,214.90