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	$71.98	7.535%	$77.4037	$77.40	$77.40	$77.40
Purchase #2	$128.52	7.789%	$138.5304	$138.53	$138.55	$138.50
Purchase #3	$56.54	7.484%	$60.7715	$60.77	$60.75	$60.80
Purchase #4	$47.38	10.654%	$52.4279	$52.43	$52.45	$52.40
Purchase #5	$181.39	8.173%	$196.215	$196.22	$196.20	$196.20
Purchase #6	$217.99	13.545%	$247.5167	$247.52	$247.50	$247.50
Purchase #7	$46.51	4.578%	$48.6392	$48.64	$48.65	$48.60
7 purchase totals =	$750.31		$821.5044	$821.51	$821.50	$821.40