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	$153.28	7.861%	$165.3293	$165.33	$165.35	$165.30
Purchase #2	$89.69	12.123%	$100.5631	$100.56	$100.55	$100.60
Purchase #3	$89.66	3.703%	$92.9801	$92.98	$93.00	$93.00
Purchase #4	$70.73	11.431%	$78.8151	$78.82	$78.80	$78.80
Purchase #5	$172.26	12.868%	$194.4264	$194.43	$194.45	$194.40
Purchase #6	$179.28	4.432%	$187.2257	$187.23	$187.25	$187.20
Purchase #7	$129.78	10.249%	$143.0812	$143.08	$143.10	$143.10
7 purchase totals =	$884.68		$962.4209	$962.43	$962.50	$962.40