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	$176.97	3.105%	$182.4649	$182.46	$182.45	$182.50
Purchase #2	$43.61	4.319%	$45.4935	$45.49	$45.50	$45.50
Purchase #3	$240.51	6.133%	$255.2605	$255.26	$255.25	$255.30
Purchase #4	$167.70	7.654%	$180.5358	$180.54	$180.55	$180.50
Purchase #5	$54.70	3.739%	$56.7452	$56.75	$56.75	$56.70
Purchase #6	$59.64	11.127%	$66.2761	$66.28	$66.30	$66.30
Purchase #7	$37.62	3.446%	$38.9164	$38.92	$38.90	$38.90
7 purchase totals =	$780.75		$825.6924	$825.70	$825.70	$825.70