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	$48.66	13.644%	$55.2992	$55.30	$55.30	$55.30
Purchase #2	$31.51	5.554%	$33.2601	$33.26	$33.25	$33.30
Purchase #3	$204.28	7.820%	$220.2547	$220.25	$220.25	$220.30
Purchase #4	$167.80	13.738%	$190.8524	$190.85	$190.85	$190.90
Purchase #5	$78.81	6.371%	$83.831	$83.83	$83.85	$83.80
Purchase #6	$245.67	4.231%	$256.0643	$256.06	$256.05	$256.10
Purchase #7	$117.46	8.503%	$127.4476	$127.45	$127.45	$127.40
7 purchase totals =	$894.19		$967.0093	$967.00	$967.00	$967.10