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	$72.35	5.393%	$76.2518	$76.25	$76.25	$76.30
Purchase #2	$157.38	13.189%	$178.1368	$178.14	$178.15	$178.10
Purchase #3	$122.83	12.850%	$138.6137	$138.61	$138.60	$138.60
Purchase #4	$20.98	6.471%	$22.3376	$22.34	$22.35	$22.30
Purchase #5	$236.43	13.678%	$268.7689	$268.77	$268.75	$268.80
Purchase #6	$56.43	9.627%	$61.8625	$61.86	$61.85	$61.90
Purchase #7	$214.44	4.408%	$223.8925	$223.89	$223.90	$223.90
7 purchase totals =	$880.84		$969.8638	$969.86	$969.85	$969.90