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	$41.65	3.257%	$43.0065	$43.01	$43.00	$43.00
Purchase #2	$113.39	13.487%	$128.6829	$128.68	$128.70	$128.70
Purchase #3	$34.76	8.653%	$37.7678	$37.77	$37.75	$37.80
Purchase #4	$54.60	12.614%	$61.4872	$61.49	$61.50	$61.50
Purchase #5	$102.76	10.453%	$113.5015	$113.50	$113.50	$113.50
Purchase #6	$38.84	10.240%	$42.8172	$42.82	$42.80	$42.80
Purchase #7	$131.34	12.809%	$148.1633	$148.16	$148.15	$148.20
7 purchase totals =	$517.34		$575.4264	$575.43	$575.40	$575.50