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	$54.88	8.366%	$59.4713	$59.47	$59.45	$59.50
Purchase #2	$155.77	6.549%	$165.9714	$165.97	$165.95	$166.00
Purchase #3	$75.83	4.155%	$78.9807	$78.98	$79.00	$79.00
Purchase #4	$169.58	12.840%	$191.3541	$191.35	$191.35	$191.40
Purchase #5	$206.90	3.538%	$214.2201	$214.22	$214.20	$214.20
Purchase #6	$12.31	10.594%	$13.6141	$13.61	$13.60	$13.60
Purchase #7	$91.49	11.525%	$102.0342	$102.03	$102.05	$102.00
7 purchase totals =	$766.76		$825.6459	$825.63	$825.60	$825.70