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	$72.47	6.841%	$77.4277	$77.43	$77.45	$77.40
Purchase #2	$48.56	4.481%	$50.736	$50.74	$50.75	$50.70
Purchase #3	$42.77	13.269%	$48.4452	$48.45	$48.45	$48.40
Purchase #4	$33.75	10.471%	$37.284	$37.28	$37.30	$37.30
Purchase #5	$71.38	10.443%	$78.8342	$78.83	$78.85	$78.80
Purchase #6	$206.35	13.376%	$233.9514	$233.95	$233.95	$234.00
Purchase #7	$250.28	10.538%	$276.6545	$276.65	$276.65	$276.70
7 purchase totals =	$725.56		$803.3330	$803.33	$803.40	$803.30