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	$177.44	6.783%	$189.4758	$189.48	$189.50	$189.50
Purchase #2	$212.75	13.324%	$241.0968	$241.10	$241.10	$241.10
Purchase #3	$57.60	9.252%	$62.9292	$62.93	$62.95	$62.90
Purchase #4	$97.89	4.714%	$102.5045	$102.50	$102.50	$102.50
Purchase #5	$227.70	12.127%	$255.3132	$255.31	$255.30	$255.30
Purchase #6	$162.68	6.288%	$172.9093	$172.91	$172.90	$172.90
Purchase #7	$143.80	5.404%	$151.571	$151.57	$151.55	$151.60
7 purchase totals =	$1,079.86		$1,175.7998	$1,175.80	$1,175.80	$1,175.80