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	$188.50	12.285%	$211.6572	$211.66	$211.65	$211.70
Purchase #2	$118.70	10.546%	$131.2181	$131.22	$131.20	$131.20
Purchase #3	$158.32	10.333%	$174.6792	$174.68	$174.70	$174.70
Purchase #4	$209.61	5.730%	$221.6207	$221.62	$221.60	$221.60
Purchase #5	$214.95	10.177%	$236.8255	$236.83	$236.85	$236.80
Purchase #6	$94.26	10.168%	$103.8444	$103.84	$103.85	$103.80
Purchase #7	$72.98	7.858%	$78.7148	$78.71	$78.70	$78.70
7 purchase totals =	$1,057.32		$1,158.5599	$1,158.56	$1,158.55	$1,158.50