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	$180.93	8.777%	$196.8102	$196.81	$196.80	$196.80
Purchase #2	$48.59	3.718%	$50.3966	$50.40	$50.40	$50.40
Purchase #3	$135.54	9.406%	$148.2889	$148.29	$148.30	$148.30
Purchase #4	$45.38	12.546%	$51.0734	$51.07	$51.05	$51.10
Purchase #5	$195.89	9.771%	$215.0304	$215.03	$215.05	$215.00
Purchase #6	$121.70	13.194%	$137.7571	$137.76	$137.75	$137.80
Purchase #7	$128.28	3.406%	$132.6492	$132.65	$132.65	$132.60
7 purchase totals =	$856.31		$932.0058	$932.01	$932.00	$932.00