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	$164.37	9.105%	$179.3359	$179.34	$179.35	$179.30
Purchase #2	$73.49	4.280%	$76.6354	$76.64	$76.65	$76.60
Purchase #3	$38.52	11.237%	$42.8485	$42.85	$42.85	$42.80
Purchase #4	$114.65	10.814%	$127.0483	$127.05	$127.05	$127.00
Purchase #5	$163.70	13.176%	$185.2691	$185.27	$185.25	$185.30
Purchase #6	$222.96	9.581%	$244.3218	$244.32	$244.30	$244.30
Purchase #7	$35.47	13.329%	$40.1978	$40.20	$40.20	$40.20
7 purchase totals =	$813.16		$895.6568	$895.67	$895.65	$895.50