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	$155.37	8.731%	$168.9354	$168.94	$168.95	$168.90
Purchase #2	$80.68	13.511%	$91.5807	$91.58	$91.60	$91.60
Purchase #3	$28.32	6.510%	$30.1636	$30.16	$30.15	$30.20
Purchase #4	$92.51	7.477%	$99.427	$99.43	$99.45	$99.40
Purchase #5	$10.31	3.204%	$10.6403	$10.64	$10.65	$10.60
Purchase #6	$28.90	3.160%	$29.8132	$29.81	$29.80	$29.80
Purchase #7	$94.83	3.809%	$98.4421	$98.44	$98.45	$98.40
7 purchase totals =	$490.92		$529.0023	$529.00	$529.05	$528.90