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	$115.72	13.425%	$131.2554	$131.26	$131.25	$131.30
Purchase #2	$87.88	3.482%	$90.94	$90.94	$90.95	$90.90
Purchase #3	$142.96	11.859%	$159.9136	$159.91	$159.90	$159.90
Purchase #4	$122.98	5.583%	$129.846	$129.85	$129.85	$129.80
Purchase #5	$227.78	7.390%	$244.6129	$244.61	$244.60	$244.60
Purchase #6	$225.74	11.479%	$251.6527	$251.65	$251.65	$251.70
Purchase #7	$51.59	3.461%	$53.3755	$53.38	$53.40	$53.40
7 purchase totals =	$974.65		$1,061.5961	$1,061.60	$1,061.60	$1,061.60