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	$91.44	13.288%	$103.5905	$103.59	$103.60	$103.60
Purchase #2	$46.35	6.705%	$49.4578	$49.46	$49.45	$49.50
Purchase #3	$148.86	9.427%	$162.893	$162.89	$162.90	$162.90
Purchase #4	$46.25	3.301%	$47.7767	$47.78	$47.80	$47.80
Purchase #5	$37.47	9.673%	$41.0945	$41.09	$41.10	$41.10
Purchase #6	$58.30	12.700%	$65.7041	$65.70	$65.70	$65.70
Purchase #7	$132.45	8.523%	$143.7387	$143.74	$143.75	$143.70
7 purchase totals =	$561.12		$614.2553	$614.25	$614.30	$614.30