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	$145.69	5.835%	$154.191	$154.19	$154.20	$154.20
Purchase #2	$18.64	10.589%	$20.6138	$20.61	$20.60	$20.60
Purchase #3	$44.74	4.139%	$46.5918	$46.59	$46.60	$46.60
Purchase #4	$154.81	11.517%	$172.6395	$172.64	$172.65	$172.60
Purchase #5	$64.52	7.683%	$69.4771	$69.48	$69.50	$69.50
Purchase #6	$148.91	13.834%	$169.5102	$169.51	$169.50	$169.50
Purchase #7	$72.56	13.232%	$82.1611	$82.16	$82.15	$82.20
7 purchase totals =	$649.87		$715.1845	$715.18	$715.20	$715.20