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	$199.64	11.160%	$221.9198	$221.92	$221.90	$221.90
Purchase #2	$241.56	12.211%	$271.0569	$271.06	$271.05	$271.10
Purchase #3	$6.31	7.700%	$6.7959	$6.80	$6.80	$6.80
Purchase #4	$195.66	12.342%	$219.8084	$219.81	$219.80	$219.80
Purchase #5	$140.71	10.563%	$155.5732	$155.57	$155.55	$155.60
Purchase #6	$122.97	3.388%	$127.1362	$127.14	$127.15	$127.10
Purchase #7	$67.42	7.239%	$72.3005	$72.30	$72.30	$72.30
7 purchase totals =	$974.27		$1,074.5909	$1,074.60	$1,074.55	$1,074.60