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	$126.33	12.409%	$142.0063	$142.01	$142.00	$142.00
Purchase #2	$195.34	9.705%	$214.2977	$214.30	$214.30	$214.30
Purchase #3	$43.89	10.143%	$48.3418	$48.34	$48.35	$48.30
Purchase #4	$111.57	12.856%	$125.9134	$125.91	$125.90	$125.90
Purchase #5	$226.56	9.323%	$247.6822	$247.68	$247.70	$247.70
Purchase #6	$215.69	4.492%	$225.3788	$225.38	$225.40	$225.40
Purchase #7	$90.39	10.839%	$100.1874	$100.19	$100.20	$100.20
7 purchase totals =	$1,009.77		$1,103.8076	$1,103.81	$1,103.85	$1,103.80