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	$84.55	9.362%	$92.4656	$92.47	$92.45	$92.50
Purchase #2	$240.77	10.638%	$266.3831	$266.38	$266.40	$266.40
Purchase #3	$241.69	3.510%	$250.1733	$250.17	$250.15	$250.20
Purchase #4	$138.27	9.626%	$151.5799	$151.58	$151.60	$151.60
Purchase #5	$41.70	5.178%	$43.8592	$43.86	$43.85	$43.90
Purchase #6	$124.91	12.227%	$140.1827	$140.18	$140.20	$140.20
Purchase #7	$84.84	6.538%	$90.3868	$90.39	$90.40	$90.40
7 purchase totals =	$956.73		$1,035.0306	$1,035.03	$1,035.05	$1,035.20