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	$90.40	4.388%	$94.3668	$94.37	$94.35	$94.40
Purchase #2	$120.28	4.756%	$126.0005	$126.00	$126.00	$126.00
Purchase #3	$129.94	9.817%	$142.6962	$142.70	$142.70	$142.70
Purchase #4	$90.32	5.635%	$95.4095	$95.41	$95.40	$95.40
Purchase #5	$27.70	13.557%	$31.4553	$31.46	$31.45	$31.50
Purchase #6	$86.78	3.774%	$90.0551	$90.06	$90.05	$90.10
Purchase #7	$184.59	10.213%	$203.4422	$203.44	$203.45	$203.40
7 purchase totals =	$730.01		$783.4256	$783.44	$783.40	$783.50