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	$217.82	4.107%	$226.7659	$226.77	$226.75	$226.80
Purchase #2	$119.83	13.162%	$135.602	$135.60	$135.60	$135.60
Purchase #3	$15.65	4.287%	$16.3209	$16.32	$16.30	$16.30
Purchase #4	$126.29	4.434%	$131.8897	$131.89	$131.90	$131.90
Purchase #5	$141.98	11.393%	$158.1558	$158.16	$158.15	$158.20
Purchase #6	$172.91	9.224%	$188.8592	$188.86	$188.85	$188.90
Purchase #7	$78.96	7.739%	$85.0707	$85.07	$85.05	$85.10
7 purchase totals =	$873.44		$942.6642	$942.67	$942.60	$942.80