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	$224.46	8.838%	$244.2978	$244.30	$244.30	$244.30
Purchase #2	$88.39	13.854%	$100.6356	$100.64	$100.65	$100.60
Purchase #3	$223.83	13.411%	$253.8478	$253.85	$253.85	$253.80
Purchase #4	$168.65	5.845%	$178.5076	$178.51	$178.50	$178.50
Purchase #5	$134.70	5.449%	$142.0398	$142.04	$142.05	$142.00
Purchase #6	$164.68	6.828%	$175.9244	$175.92	$175.90	$175.90
Purchase #7	$81.44	5.727%	$86.1041	$86.10	$86.10	$86.10
7 purchase totals =	$1,086.15		$1,181.3571	$1,181.36	$1,181.35	$1,181.20