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	$199.48	11.738%	$222.895	$222.90	$222.90	$222.90
Purchase #2	$42.56	13.205%	$48.18	$48.18	$48.20	$48.20
Purchase #3	$144.36	11.734%	$161.2992	$161.30	$161.30	$161.30
Purchase #4	$81.49	9.597%	$89.3106	$89.31	$89.30	$89.30
Purchase #5	$224.30	12.602%	$252.5663	$252.57	$252.55	$252.60
Purchase #6	$128.29	4.554%	$134.1323	$134.13	$134.15	$134.10
Purchase #7	$100.76	7.202%	$108.0167	$108.02	$108.00	$108.00
7 purchase totals =	$921.24		$1,016.4001	$1,016.41	$1,016.40	$1,016.40