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	$55.84	10.332%	$61.6094	$61.61	$61.60	$61.60
Purchase #2	$80.38	13.768%	$91.4467	$91.45	$91.45	$91.40
Purchase #3	$195.96	9.182%	$213.953	$213.95	$213.95	$214.00
Purchase #4	$76.95	12.450%	$86.5303	$86.53	$86.55	$86.50
Purchase #5	$90.95	4.830%	$95.3429	$95.34	$95.35	$95.30
Purchase #6	$173.40	6.788%	$185.1704	$185.17	$185.15	$185.20
Purchase #7	$166.31	7.174%	$178.2411	$178.24	$178.25	$178.20
7 purchase totals =	$839.79		$912.2938	$912.29	$912.30	$912.20