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	$113.28	7.533%	$121.8134	$121.81	$121.80	$121.80
Purchase #2	$105.56	5.631%	$111.5041	$111.50	$111.50	$111.50
Purchase #3	$191.65	4.669%	$200.5981	$200.60	$200.60	$200.60
Purchase #4	$188.47	6.341%	$200.4209	$200.42	$200.40	$200.40
Purchase #5	$224.51	12.835%	$253.3259	$253.33	$253.35	$253.30
Purchase #6	$116.38	13.181%	$131.72	$131.72	$131.70	$131.70
Purchase #7	$171.70	5.772%	$181.6105	$181.61	$181.60	$181.60
7 purchase totals =	$1,111.55		$1,200.9929	$1,200.99	$1,200.95	$1,200.90