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	$207.77	7.158%	$222.6422	$222.64	$222.65	$222.60
Purchase #2	$110.59	5.270%	$116.4181	$116.42	$116.40	$116.40
Purchase #3	$109.42	8.684%	$118.922	$118.92	$118.90	$118.90
Purchase #4	$36.93	7.183%	$39.5827	$39.58	$39.60	$39.60
Purchase #5	$66.58	9.615%	$72.9817	$72.98	$73.00	$73.00
Purchase #6	$236.78	4.362%	$247.1083	$247.11	$247.10	$247.10
Purchase #7	$227.74	12.308%	$255.7702	$255.77	$255.75	$255.80
7 purchase totals =	$995.81		$1,073.4252	$1,073.42	$1,073.40	$1,073.40