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	$165.72	11.839%	$185.3396	$185.34	$185.35	$185.30
Purchase #2	$7.94	12.673%	$8.9462	$8.95	$8.95	$8.90
Purchase #3	$236.94	3.353%	$244.8846	$244.88	$244.90	$244.90
Purchase #4	$202.57	9.874%	$222.5718	$222.57	$222.55	$222.60
Purchase #5	$58.37	13.293%	$66.1291	$66.13	$66.15	$66.10
Purchase #6	$226.92	13.726%	$258.067	$258.07	$258.05	$258.10
Purchase #7	$117.94	10.783%	$130.6575	$130.66	$130.65	$130.70
7 purchase totals =	$1,016.40		$1,116.5958	$1,116.60	$1,116.60	$1,116.60