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	$180.53	11.266%	$200.8685	$200.87	$200.85	$200.90
Purchase #2	$132.69	3.358%	$137.1457	$137.15	$137.15	$137.10
Purchase #3	$56.64	5.508%	$59.7597	$59.76	$59.75	$59.80
Purchase #4	$148.95	9.289%	$162.786	$162.79	$162.80	$162.80
Purchase #5	$207.61	10.118%	$228.616	$228.62	$228.60	$228.60
Purchase #6	$172.68	3.458%	$178.6513	$178.65	$178.65	$178.70
Purchase #7	$202.49	9.760%	$222.253	$222.25	$222.25	$222.30
7 purchase totals =	$1,101.59		$1,190.0802	$1,190.09	$1,190.05	$1,190.20