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	$202.92	5.705%	$214.4966	$214.50	$214.50	$214.50
Purchase #2	$88.30	13.102%	$99.8691	$99.87	$99.85	$99.90
Purchase #3	$197.31	6.783%	$210.6935	$210.69	$210.70	$210.70
Purchase #4	$224.50	13.809%	$255.5012	$255.50	$255.50	$255.50
Purchase #5	$153.84	7.158%	$164.8519	$164.85	$164.85	$164.90
Purchase #6	$36.90	4.537%	$38.5742	$38.57	$38.55	$38.60
Purchase #7	$144.95	13.583%	$164.6386	$164.64	$164.65	$164.60
7 purchase totals =	$1,048.72		$1,148.6251	$1,148.62	$1,148.60	$1,148.70