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	$48.63	4.722%	$50.9263	$50.93	$50.95	$50.90
Purchase #2	$231.89	4.546%	$242.4317	$242.43	$242.45	$242.40
Purchase #3	$43.90	7.675%	$47.2693	$47.27	$47.25	$47.30
Purchase #4	$57.92	13.666%	$65.8353	$65.84	$65.85	$65.80
Purchase #5	$40.46	10.495%	$44.7063	$44.71	$44.70	$44.70
Purchase #6	$59.39	10.477%	$65.6123	$65.61	$65.60	$65.60
Purchase #7	$171.28	9.630%	$187.7743	$187.77	$187.75	$187.80
7 purchase totals =	$653.47		$704.5555	$704.56	$704.55	$704.50