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	$80.51	13.827%	$91.6421	$91.64	$91.65	$91.60
Purchase #2	$134.37	8.853%	$146.2658	$146.27	$146.25	$146.30
Purchase #3	$46.25	8.674%	$50.2617	$50.26	$50.25	$50.30
Purchase #4	$202.52	9.295%	$221.3442	$221.34	$221.35	$221.30
Purchase #5	$200.73	7.164%	$215.1103	$215.11	$215.10	$215.10
Purchase #6	$217.34	4.396%	$226.8943	$226.89	$226.90	$226.90
Purchase #7	$137.94	11.586%	$153.9217	$153.92	$153.90	$153.90
7 purchase totals =	$1,019.66		$1,105.4401	$1,105.43	$1,105.40	$1,105.40