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	$206.55	7.515%	$222.0722	$222.07	$222.05	$222.10
Purchase #2	$55.28	3.784%	$57.3718	$57.37	$57.35	$57.40
Purchase #3	$174.38	13.634%	$198.155	$198.16	$198.15	$198.20
Purchase #4	$6.90	8.290%	$7.472	$7.47	$7.45	$7.50
Purchase #5	$6.45	4.669%	$6.7512	$6.75	$6.75	$6.80
Purchase #6	$216.96	11.320%	$241.5199	$241.52	$241.50	$241.50
Purchase #7	$70.74	10.635%	$78.2632	$78.26	$78.25	$78.30
7 purchase totals =	$737.26		$811.6053	$811.60	$811.50	$811.80