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	$101.30	9.226%	$110.6459	$110.65	$110.65	$110.60
Purchase #2	$19.27	9.401%	$21.0816	$21.08	$21.10	$21.10
Purchase #3	$99.34	11.828%	$111.0899	$111.09	$111.10	$111.10
Purchase #4	$120.92	5.132%	$127.1256	$127.13	$127.15	$127.10
Purchase #5	$69.39	6.825%	$74.1259	$74.13	$74.15	$74.10
Purchase #6	$141.54	3.592%	$146.6241	$146.62	$146.60	$146.60
Purchase #7	$250.97	5.206%	$264.0355	$264.04	$264.05	$264.00
7 purchase totals =	$802.73		$854.7285	$854.74	$854.80	$854.60