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	$225.92	6.153%	$239.8209	$239.82	$239.80	$239.80
Purchase #2	$21.82	8.208%	$23.611	$23.61	$23.60	$23.60
Purchase #3	$245.69	12.707%	$276.9098	$276.91	$276.90	$276.90
Purchase #4	$220.74	13.375%	$250.264	$250.26	$250.25	$250.30
Purchase #5	$95.65	4.238%	$99.7036	$99.70	$99.70	$99.70
Purchase #6	$140.72	4.152%	$146.5627	$146.56	$146.55	$146.60
Purchase #7	$127.27	3.175%	$131.3108	$131.31	$131.30	$131.30
7 purchase totals =	$1,077.81		$1,168.1828	$1,168.17	$1,168.10	$1,168.20