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	$75.29	4.436%	$78.6299	$78.63	$78.65	$78.60
Purchase #2	$70.25	5.189%	$73.8953	$73.90	$73.90	$73.90
Purchase #3	$150.91	8.841%	$164.252	$164.25	$164.25	$164.30
Purchase #4	$8.29	13.606%	$9.4179	$9.42	$9.40	$9.40
Purchase #5	$30.87	6.357%	$32.8324	$32.83	$32.85	$32.80
Purchase #6	$215.96	3.547%	$223.6201	$223.62	$223.60	$223.60
Purchase #7	$94.38	9.854%	$103.6802	$103.68	$103.70	$103.70
7 purchase totals =	$645.95		$686.3278	$686.33	$686.35	$686.30