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	$215.26	9.848%	$236.4588	$236.46	$236.45	$236.50
Purchase #2	$234.28	10.179%	$258.1274	$258.13	$258.15	$258.10
Purchase #3	$229.54	5.162%	$241.3889	$241.39	$241.40	$241.40
Purchase #4	$90.27	13.104%	$102.099	$102.10	$102.10	$102.10
Purchase #5	$69.54	12.635%	$78.3264	$78.33	$78.35	$78.30
Purchase #6	$188.46	6.624%	$200.9436	$200.94	$200.95	$200.90
Purchase #7	$171.63	11.354%	$191.1169	$191.12	$191.10	$191.10
7 purchase totals =	$1,198.98		$1,308.4610	$1,308.47	$1,308.50	$1,308.40