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	$126.33	13.807%	$143.7724	$143.77	$143.75	$143.80
Purchase #2	$226.32	12.575%	$254.7797	$254.78	$254.80	$254.80
Purchase #3	$120.80	12.291%	$135.6475	$135.65	$135.65	$135.60
Purchase #4	$137.33	7.373%	$147.4553	$147.46	$147.45	$147.50
Purchase #5	$99.92	11.555%	$111.4658	$111.47	$111.45	$111.50
Purchase #6	$45.43	6.548%	$48.4048	$48.40	$48.40	$48.40
Purchase #7	$51.33	7.159%	$55.0047	$55.00	$55.00	$55.00
7 purchase totals =	$807.46		$896.5302	$896.53	$896.50	$896.60