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	$221.81	12.851%	$250.3148	$250.31	$250.30	$250.30
Purchase #2	$29.79	5.152%	$31.3248	$31.32	$31.30	$31.30
Purchase #3	$19.81	12.296%	$22.2458	$22.25	$22.25	$22.20
Purchase #4	$59.77	11.680%	$66.7511	$66.75	$66.75	$66.80
Purchase #5	$96.67	3.772%	$100.3164	$100.32	$100.30	$100.30
Purchase #6	$57.81	4.212%	$60.245	$60.25	$60.25	$60.20
Purchase #7	$174.68	7.365%	$187.5452	$187.55	$187.55	$187.50
7 purchase totals =	$660.34		$718.7431	$718.75	$718.70	$718.60