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	$71.28	9.834%	$78.2897	$78.29	$78.30	$78.30
Purchase #2	$190.49	13.102%	$215.448	$215.45	$215.45	$215.40
Purchase #3	$91.66	5.827%	$97.001	$97.00	$97.00	$97.00
Purchase #4	$18.81	3.486%	$19.4657	$19.47	$19.45	$19.50
Purchase #5	$72.92	13.843%	$83.0143	$83.01	$83.00	$83.00
Purchase #6	$22.41	13.678%	$25.4752	$25.48	$25.50	$25.50
Purchase #7	$141.48	12.106%	$158.6076	$158.61	$158.60	$158.60
7 purchase totals =	$609.05		$677.3015	$677.31	$677.30	$677.30