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	$227.81	11.725%	$254.5207	$254.52	$254.50	$254.50
Purchase #2	$60.42	3.281%	$62.4024	$62.40	$62.40	$62.40
Purchase #3	$231.30	4.214%	$241.047	$241.05	$241.05	$241.00
Purchase #4	$233.76	11.179%	$259.892	$259.89	$259.90	$259.90
Purchase #5	$112.25	5.176%	$118.0601	$118.06	$118.05	$118.10
Purchase #6	$46.75	10.682%	$51.7438	$51.74	$51.75	$51.70
Purchase #7	$49.37	5.720%	$52.194	$52.19	$52.20	$52.20
7 purchase totals =	$961.66		$1,039.8600	$1,039.85	$1,039.85	$1,039.80