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	$210.70	8.859%	$229.3659	$229.37	$229.35	$229.40
Purchase #2	$160.95	9.285%	$175.8942	$175.89	$175.90	$175.90
Purchase #3	$226.52	4.788%	$237.3658	$237.37	$237.35	$237.40
Purchase #4	$161.26	6.849%	$172.3047	$172.30	$172.30	$172.30
Purchase #5	$184.54	13.138%	$208.7849	$208.78	$208.80	$208.80
Purchase #6	$228.47	4.389%	$238.4975	$238.50	$238.50	$238.50
Purchase #7	$174.98	12.494%	$196.842	$196.84	$196.85	$196.80
7 purchase totals =	$1,347.42		$1,459.0550	$1,459.05	$1,459.05	$1,459.10