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	$205.45	5.288%	$216.3142	$216.31	$216.30	$216.30
Purchase #2	$196.35	4.664%	$205.5078	$205.51	$205.50	$205.50
Purchase #3	$228.31	3.259%	$235.7506	$235.75	$235.75	$235.80
Purchase #4	$225.70	12.503%	$253.9193	$253.92	$253.90	$253.90
Purchase #5	$48.50	12.114%	$54.3753	$54.38	$54.40	$54.40
Purchase #6	$94.40	6.310%	$100.3566	$100.36	$100.35	$100.40
Purchase #7	$16.34	5.574%	$17.2508	$17.25	$17.25	$17.30
7 purchase totals =	$1,015.05		$1,083.4746	$1,083.48	$1,083.45	$1,083.60