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	$43.55	11.308%	$48.4746	$48.47	$48.45	$48.50
Purchase #2	$133.81	4.741%	$140.1539	$140.15	$140.15	$140.20
Purchase #3	$213.85	12.821%	$241.2677	$241.27	$241.25	$241.30
Purchase #4	$163.32	11.271%	$181.7278	$181.73	$181.75	$181.70
Purchase #5	$83.71	12.489%	$94.1645	$94.16	$94.15	$94.20
Purchase #6	$151.37	11.397%	$168.6216	$168.62	$168.60	$168.60
Purchase #7	$146.62	3.241%	$151.372	$151.37	$151.35	$151.40
7 purchase totals =	$936.23		$1,025.7821	$1,025.77	$1,025.70	$1,025.90