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	$102.55	5.400%	$108.0877	$108.09	$108.10	$108.10
Purchase #2	$29.78	9.767%	$32.6886	$32.69	$32.70	$32.70
Purchase #3	$146.52	4.164%	$152.6211	$152.62	$152.60	$152.60
Purchase #4	$213.36	11.619%	$238.1503	$238.15	$238.15	$238.20
Purchase #5	$134.59	6.598%	$143.4702	$143.47	$143.45	$143.50
Purchase #6	$85.77	6.272%	$91.1495	$91.15	$91.15	$91.10
Purchase #7	$207.28	13.802%	$235.8888	$235.89	$235.90	$235.90
7 purchase totals =	$919.85		$1,002.0562	$1,002.06	$1,002.05	$1,002.10