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	$224.29	5.163%	$235.8701	$235.87	$235.85	$235.90
Purchase #2	$87.41	6.837%	$93.3862	$93.39	$93.40	$93.40
Purchase #3	$51.56	9.153%	$56.2793	$56.28	$56.30	$56.30
Purchase #4	$149.56	11.330%	$166.5051	$166.51	$166.50	$166.50
Purchase #5	$57.29	9.649%	$62.8179	$62.82	$62.80	$62.80
Purchase #6	$103.84	7.537%	$111.6664	$111.67	$111.65	$111.70
Purchase #7	$132.89	13.253%	$150.5019	$150.50	$150.50	$150.50
7 purchase totals =	$806.84		$877.0269	$877.04	$877.00	$877.10