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	$39.46	11.431%	$43.9707	$43.97	$43.95	$44.00
Purchase #2	$156.83	4.679%	$164.1681	$164.17	$164.15	$164.20
Purchase #3	$55.92	13.375%	$63.3993	$63.40	$63.40	$63.40
Purchase #4	$106.76	4.859%	$111.9475	$111.95	$111.95	$111.90
Purchase #5	$48.40	4.363%	$50.5117	$50.51	$50.50	$50.50
Purchase #6	$217.53	11.117%	$241.7128	$241.71	$241.70	$241.70
Purchase #7	$94.48	6.161%	$100.3009	$100.30	$100.30	$100.30
7 purchase totals =	$719.38		$776.0110	$776.01	$775.95	$776.00