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	$243.72	8.759%	$265.0674	$265.07	$265.05	$265.10
Purchase #2	$34.68	9.364%	$37.9274	$37.93	$37.95	$37.90
Purchase #3	$216.47	7.765%	$233.2789	$233.28	$233.30	$233.30
Purchase #4	$126.57	13.843%	$144.0911	$144.09	$144.10	$144.10
Purchase #5	$104.61	12.710%	$117.9059	$117.91	$117.90	$117.90
Purchase #6	$143.51	3.671%	$148.7783	$148.78	$148.80	$148.80
Purchase #7	$92.53	3.411%	$95.6862	$95.69	$95.70	$95.70
7 purchase totals =	$962.09		$1,042.7352	$1,042.75	$1,042.80	$1,042.80