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	$90.76	5.294%	$95.5648	$95.56	$95.55	$95.60
Purchase #2	$238.96	9.427%	$261.4868	$261.49	$261.50	$261.50
Purchase #3	$232.65	5.141%	$244.6105	$244.61	$244.60	$244.60
Purchase #4	$170.75	5.390%	$179.9534	$179.95	$179.95	$180.00
Purchase #5	$6.53	9.607%	$7.1573	$7.16	$7.15	$7.20
Purchase #6	$203.61	3.363%	$210.4574	$210.46	$210.45	$210.50
Purchase #7	$116.66	10.176%	$128.5313	$128.53	$128.55	$128.50
7 purchase totals =	$1,059.92		$1,127.7615	$1,127.76	$1,127.75	$1,127.90