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	$153.66	12.258%	$172.4956	$172.50	$172.50	$172.50
Purchase #2	$165.63	11.326%	$184.3893	$184.39	$184.40	$184.40
Purchase #3	$138.84	3.275%	$143.387	$143.39	$143.40	$143.40
Purchase #4	$152.75	3.703%	$158.4063	$158.41	$158.40	$158.40
Purchase #5	$92.37	3.134%	$95.2649	$95.26	$95.25	$95.30
Purchase #6	$215.25	8.476%	$233.4946	$233.49	$233.50	$233.50
Purchase #7	$157.54	10.643%	$174.307	$174.31	$174.30	$174.30
7 purchase totals =	$1,076.04		$1,161.7447	$1,161.75	$1,161.75	$1,161.80