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	$150.95	6.577%	$160.878	$160.88	$160.90	$160.90
Purchase #2	$105.53	6.567%	$112.4602	$112.46	$112.45	$112.50
Purchase #3	$218.85	11.835%	$244.7509	$244.75	$244.75	$244.80
Purchase #4	$80.25	12.874%	$90.5814	$90.58	$90.60	$90.60
Purchase #5	$241.70	7.858%	$260.6928	$260.69	$260.70	$260.70
Purchase #6	$223.58	6.784%	$238.7477	$238.75	$238.75	$238.70
Purchase #7	$71.69	7.427%	$77.0144	$77.01	$77.00	$77.00
7 purchase totals =	$1,092.55		$1,185.1254	$1,185.12	$1,185.15	$1,185.20