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	$118.47	7.576%	$127.4453	$127.45	$127.45	$127.40
Purchase #2	$135.26	9.591%	$148.2328	$148.23	$148.25	$148.20
Purchase #3	$196.90	12.243%	$221.0065	$221.01	$221.00	$221.00
Purchase #4	$107.72	13.324%	$122.0726	$122.07	$122.05	$122.10
Purchase #5	$215.83	3.278%	$222.9049	$222.90	$222.90	$222.90
Purchase #6	$65.28	4.620%	$68.2959	$68.30	$68.30	$68.30
Purchase #7	$89.48	5.716%	$94.5947	$94.59	$94.60	$94.60
7 purchase totals =	$928.94		$1,004.5527	$1,004.55	$1,004.55	$1,004.50