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	$20.62	11.864%	$23.0664	$23.07	$23.05	$23.10
Purchase #2	$230.59	11.179%	$256.3677	$256.37	$256.35	$256.40
Purchase #3	$84.50	7.329%	$90.693	$90.69	$90.70	$90.70
Purchase #4	$164.69	10.792%	$182.4633	$182.46	$182.45	$182.50
Purchase #5	$91.34	13.251%	$103.4435	$103.44	$103.45	$103.40
Purchase #6	$151.64	9.322%	$165.7759	$165.78	$165.80	$165.80
Purchase #7	$118.70	10.466%	$131.1231	$131.12	$131.10	$131.10
7 purchase totals =	$862.08		$952.9329	$952.93	$952.90	$953.00