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	$231.73	7.763%	$249.7192	$249.72	$249.70	$249.70
Purchase #2	$35.74	6.720%	$38.1417	$38.14	$38.15	$38.10
Purchase #3	$126.58	3.544%	$131.066	$131.07	$131.05	$131.10
Purchase #4	$224.52	8.506%	$243.6177	$243.62	$243.60	$243.60
Purchase #5	$176.28	8.338%	$190.9782	$190.98	$191.00	$191.00
Purchase #6	$144.67	10.290%	$159.5565	$159.56	$159.55	$159.60
Purchase #7	$119.64	3.533%	$123.8669	$123.87	$123.85	$123.90
7 purchase totals =	$1,059.16		$1,136.9462	$1,136.96	$1,136.90	$1,137.00