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	$146.87	10.829%	$162.7746	$162.77	$162.75	$162.80
Purchase #2	$221.62	7.446%	$238.1218	$238.12	$238.10	$238.10
Purchase #3	$220.28	12.149%	$247.0418	$247.04	$247.05	$247.00
Purchase #4	$106.46	8.548%	$115.5602	$115.56	$115.55	$115.60
Purchase #5	$17.31	5.814%	$18.3164	$18.32	$18.30	$18.30
Purchase #6	$240.63	4.505%	$251.4704	$251.47	$251.45	$251.50
Purchase #7	$52.60	13.819%	$59.8688	$59.87	$59.85	$59.90
7 purchase totals =	$1,005.77		$1,093.1540	$1,093.15	$1,093.05	$1,093.20