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	$9.68	5.856%	$10.2469	$10.25	$10.25	$10.20
Purchase #2	$59.45	12.593%	$66.9365	$66.94	$66.95	$66.90
Purchase #3	$61.98	7.315%	$66.5138	$66.51	$66.50	$66.50
Purchase #4	$148.40	7.799%	$159.9737	$159.97	$159.95	$160.00
Purchase #5	$118.30	13.120%	$133.821	$133.82	$133.80	$133.80
Purchase #6	$241.32	5.455%	$254.484	$254.48	$254.50	$254.50
Purchase #7	$38.81	5.373%	$40.8953	$40.90	$40.90	$40.90
7 purchase totals =	$677.94		$732.8712	$732.87	$732.85	$732.80