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	$94.95	5.609%	$100.2757	$100.28	$100.30	$100.30
Purchase #2	$40.72	12.795%	$45.9301	$45.93	$45.95	$45.90
Purchase #3	$21.83	5.780%	$23.0918	$23.09	$23.10	$23.10
Purchase #4	$96.91	6.431%	$103.1423	$103.14	$103.15	$103.10
Purchase #5	$43.34	11.406%	$48.2834	$48.28	$48.30	$48.30
Purchase #6	$74.74	9.332%	$81.7147	$81.71	$81.70	$81.70
Purchase #7	$42.29	6.449%	$45.0173	$45.02	$45.00	$45.00
7 purchase totals =	$414.78		$447.4553	$447.45	$447.50	$447.40