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	$65.31	13.787%	$74.3143	$74.31	$74.30	$74.30
Purchase #2	$241.92	13.423%	$274.3929	$274.39	$274.40	$274.40
Purchase #3	$37.84	7.315%	$40.608	$40.61	$40.60	$40.60
Purchase #4	$211.45	4.761%	$221.5171	$221.52	$221.50	$221.50
Purchase #5	$124.35	6.268%	$132.1443	$132.14	$132.15	$132.10
Purchase #6	$53.39	6.524%	$56.8732	$56.87	$56.85	$56.90
Purchase #7	$119.88	10.489%	$132.4542	$132.45	$132.45	$132.50
7 purchase totals =	$854.14		$932.3040	$932.29	$932.25	$932.30