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	$225.41	4.509%	$235.5737	$235.57	$235.55	$235.60
Purchase #2	$46.89	11.345%	$52.2097	$52.21	$52.20	$52.20
Purchase #3	$26.84	4.459%	$28.0368	$28.04	$28.05	$28.00
Purchase #4	$85.60	3.778%	$88.834	$88.83	$88.85	$88.80
Purchase #5	$33.38	13.162%	$37.7735	$37.77	$37.75	$37.80
Purchase #6	$173.33	9.461%	$189.7288	$189.73	$189.75	$189.70
Purchase #7	$59.94	10.760%	$66.3895	$66.39	$66.40	$66.40
7 purchase totals =	$651.39		$698.5460	$698.54	$698.55	$698.50