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	$140.25	8.446%	$152.0955	$152.10	$152.10	$152.10
Purchase #2	$214.95	3.236%	$221.9058	$221.91	$221.90	$221.90
Purchase #3	$166.56	13.173%	$188.5009	$188.50	$188.50	$188.50
Purchase #4	$180.74	3.821%	$187.6461	$187.65	$187.65	$187.60
Purchase #5	$158.53	13.510%	$179.9474	$179.95	$179.95	$179.90
Purchase #6	$220.78	11.618%	$246.4302	$246.43	$246.45	$246.40
Purchase #7	$46.69	13.585%	$53.0328	$53.03	$53.05	$53.00
7 purchase totals =	$1,128.50		$1,229.5587	$1,229.57	$1,229.60	$1,229.40