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	$132.61	8.567%	$143.9707	$143.97	$143.95	$144.00
Purchase #2	$128.81	6.507%	$137.1917	$137.19	$137.20	$137.20
Purchase #3	$30.43	3.587%	$31.5215	$31.52	$31.50	$31.50
Purchase #4	$67.53	12.609%	$76.0449	$76.04	$76.05	$76.00
Purchase #5	$86.87	6.476%	$92.4957	$92.50	$92.50	$92.50
Purchase #6	$133.45	11.183%	$148.3737	$148.37	$148.35	$148.40
Purchase #7	$107.68	3.388%	$111.3282	$111.33	$111.35	$111.30
7 purchase totals =	$687.38		$740.9264	$740.92	$740.90	$740.90