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	$68.28	5.564%	$72.0791	$72.08	$72.10	$72.10
Purchase #2	$32.62	10.806%	$36.1449	$36.14	$36.15	$36.10
Purchase #3	$6.93	11.439%	$7.7227	$7.72	$7.70	$7.70
Purchase #4	$45.76	3.448%	$47.3378	$47.34	$47.35	$47.30
Purchase #5	$119.52	3.177%	$123.3172	$123.32	$123.30	$123.30
Purchase #6	$176.60	11.721%	$197.2993	$197.30	$197.30	$197.30
Purchase #7	$71.83	9.784%	$78.8578	$78.86	$78.85	$78.90
7 purchase totals =	$521.54		$562.7588	$562.76	$562.75	$562.70