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	$162.77	4.819%	$170.6139	$170.61	$170.60	$170.60
Purchase #2	$52.69	9.433%	$57.6602	$57.66	$57.65	$57.70
Purchase #3	$168.73	9.703%	$185.1019	$185.10	$185.10	$185.10
Purchase #4	$160.66	9.774%	$176.3629	$176.36	$176.35	$176.40
Purchase #5	$198.55	13.587%	$225.527	$225.53	$225.55	$225.50
Purchase #6	$217.34	3.861%	$225.7315	$225.73	$225.75	$225.70
Purchase #7	$104.78	12.151%	$117.5118	$117.51	$117.50	$117.50
7 purchase totals =	$1,065.52		$1,158.5092	$1,158.50	$1,158.50	$1,158.50