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	$43.49	11.830%	$48.6349	$48.63	$48.65	$48.60
Purchase #2	$170.29	12.326%	$191.2799	$191.28	$191.30	$191.30
Purchase #3	$228.39	13.725%	$259.7365	$259.74	$259.75	$259.70
Purchase #4	$51.31	6.696%	$54.7457	$54.75	$54.75	$54.70
Purchase #5	$79.89	3.628%	$82.7884	$82.79	$82.80	$82.80
Purchase #6	$95.74	9.806%	$105.1283	$105.13	$105.15	$105.10
Purchase #7	$218.78	6.821%	$233.703	$233.70	$233.70	$233.70
7 purchase totals =	$887.89		$976.0167	$976.02	$976.10	$975.90