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	$157.89	8.694%	$171.617	$171.62	$171.60	$171.60
Purchase #2	$182.31	7.610%	$196.1838	$196.18	$196.20	$196.20
Purchase #3	$153.92	5.861%	$162.9413	$162.94	$162.95	$162.90
Purchase #4	$248.93	11.305%	$277.0715	$277.07	$277.05	$277.10
Purchase #5	$47.98	12.644%	$54.0466	$54.05	$54.05	$54.00
Purchase #6	$144.68	4.193%	$150.7464	$150.75	$150.75	$150.70
Purchase #7	$102.98	7.320%	$110.5181	$110.52	$110.50	$110.50
7 purchase totals =	$1,038.69		$1,123.1247	$1,123.13	$1,123.10	$1,123.00