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	$207.40	11.421%	$231.0872	$231.09	$231.10	$231.10
Purchase #2	$68.54	11.128%	$76.1671	$76.17	$76.15	$76.20
Purchase #3	$212.84	5.171%	$223.846	$223.85	$223.85	$223.80
Purchase #4	$33.55	5.872%	$35.5201	$35.52	$35.50	$35.50
Purchase #5	$114.93	10.540%	$127.0436	$127.04	$127.05	$127.00
Purchase #6	$29.90	8.764%	$32.5204	$32.52	$32.50	$32.50
Purchase #7	$175.29	7.283%	$188.0564	$188.06	$188.05	$188.10
7 purchase totals =	$842.45		$914.2408	$914.25	$914.20	$914.20