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	$50.35	7.548%	$54.1504	$54.15	$54.15	$54.20
Purchase #2	$130.33	10.537%	$144.0629	$144.06	$144.05	$144.10
Purchase #3	$68.49	6.537%	$72.9672	$72.97	$72.95	$73.00
Purchase #4	$214.96	4.284%	$224.1689	$224.17	$224.15	$224.20
Purchase #5	$109.72	12.683%	$123.6358	$123.64	$123.65	$123.60
Purchase #6	$29.78	8.155%	$32.2086	$32.21	$32.20	$32.20
Purchase #7	$247.92	3.619%	$256.8922	$256.89	$256.90	$256.90
7 purchase totals =	$851.55		$908.0860	$908.09	$908.05	$908.20