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	$103.73	7.732%	$111.7504	$111.75	$111.75	$111.80
Purchase #2	$217.43	11.645%	$242.7497	$242.75	$242.75	$242.70
Purchase #3	$198.82	3.502%	$205.7827	$205.78	$205.80	$205.80
Purchase #4	$93.68	6.865%	$100.1111	$100.11	$100.10	$100.10
Purchase #5	$133.47	7.277%	$143.1826	$143.18	$143.20	$143.20
Purchase #6	$111.49	6.140%	$118.3355	$118.34	$118.35	$118.30
Purchase #7	$107.75	4.213%	$112.2895	$112.29	$112.30	$112.30
7 purchase totals =	$966.37		$1,034.2015	$1,034.20	$1,034.25	$1,034.20