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	$165.70	4.600%	$173.3222	$173.32	$173.30	$173.30
Purchase #2	$239.42	9.516%	$262.2032	$262.20	$262.20	$262.20
Purchase #3	$130.61	13.708%	$148.514	$148.51	$148.50	$148.50
Purchase #4	$160.39	5.302%	$168.8939	$168.89	$168.90	$168.90
Purchase #5	$142.59	13.482%	$161.814	$161.81	$161.80	$161.80
Purchase #6	$151.30	4.531%	$158.1554	$158.16	$158.15	$158.20
Purchase #7	$18.78	7.423%	$20.174	$20.17	$20.15	$20.20
7 purchase totals =	$1,008.79		$1,093.0767	$1,093.06	$1,093.00	$1,093.10