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	$130.87	10.231%	$144.2593	$144.26	$144.25	$144.30
Purchase #2	$220.67	5.834%	$233.5439	$233.54	$233.55	$233.50
Purchase #3	$202.88	5.789%	$214.6247	$214.62	$214.60	$214.60
Purchase #4	$217.33	11.706%	$242.7706	$242.77	$242.75	$242.80
Purchase #5	$25.60	12.742%	$28.862	$28.86	$28.85	$28.90
Purchase #6	$101.58	9.358%	$111.0859	$111.09	$111.10	$111.10
Purchase #7	$44.44	7.774%	$47.8948	$47.89	$47.90	$47.90
7 purchase totals =	$943.37		$1,023.0412	$1,023.03	$1,023.00	$1,023.10