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	$226.90	9.334%	$248.0788	$248.08	$248.10	$248.10
Purchase #2	$98.79	6.583%	$105.2933	$105.29	$105.30	$105.30
Purchase #3	$195.45	4.429%	$204.1065	$204.11	$204.10	$204.10
Purchase #4	$16.81	11.328%	$18.7142	$18.71	$18.70	$18.70
Purchase #5	$100.54	11.169%	$111.7693	$111.77	$111.75	$111.80
Purchase #6	$116.75	5.545%	$123.2238	$123.22	$123.20	$123.20
Purchase #7	$250.81	12.294%	$281.6446	$281.64	$281.65	$281.60
7 purchase totals =	$1,006.05		$1,092.8305	$1,092.82	$1,092.80	$1,092.80