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	$111.93	12.810%	$126.2682	$126.27	$126.25	$126.30
Purchase #2	$151.87	8.495%	$164.7714	$164.77	$164.75	$164.80
Purchase #3	$229.90	13.401%	$260.7089	$260.71	$260.70	$260.70
Purchase #4	$67.54	6.791%	$72.1266	$72.13	$72.15	$72.10
Purchase #5	$234.72	11.435%	$261.5602	$261.56	$261.55	$261.60
Purchase #6	$107.66	8.235%	$116.5258	$116.53	$116.55	$116.50
Purchase #7	$86.62	6.252%	$92.0355	$92.04	$92.05	$92.00
7 purchase totals =	$990.24		$1,093.9966	$1,094.01	$1,094.00	$1,094.00