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	$211.31	5.497%	$222.9257	$222.93	$222.95	$222.90
Purchase #2	$196.81	12.117%	$220.6575	$220.66	$220.65	$220.70
Purchase #3	$10.68	10.587%	$11.8107	$11.81	$11.80	$11.80
Purchase #4	$73.87	7.533%	$79.4346	$79.43	$79.45	$79.40
Purchase #5	$210.59	7.451%	$226.2811	$226.28	$226.30	$226.30
Purchase #6	$147.77	13.532%	$167.7662	$167.77	$167.75	$167.80
Purchase #7	$138.59	10.111%	$152.6028	$152.60	$152.60	$152.60
7 purchase totals =	$989.62		$1,081.4786	$1,081.48	$1,081.50	$1,081.50