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	$199.80	5.207%	$210.2036	$210.20	$210.20	$210.20
Purchase #2	$72.35	7.428%	$77.7242	$77.72	$77.70	$77.70
Purchase #3	$200.80	12.499%	$225.898	$225.90	$225.90	$225.90
Purchase #4	$17.34	6.303%	$18.4329	$18.43	$18.45	$18.40
Purchase #5	$31.66	9.782%	$34.757	$34.76	$34.75	$34.80
Purchase #6	$75.91	3.472%	$78.5456	$78.55	$78.55	$78.50
Purchase #7	$127.43	13.482%	$144.6101	$144.61	$144.60	$144.60
7 purchase totals =	$725.29		$790.1714	$790.17	$790.15	$790.10