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	$71.89	13.282%	$81.4384	$81.44	$81.45	$81.40
Purchase #2	$94.76	11.342%	$105.5077	$105.51	$105.50	$105.50
Purchase #3	$21.76	5.354%	$22.925	$22.93	$22.95	$22.90
Purchase #4	$42.93	10.621%	$47.4896	$47.49	$47.50	$47.50
Purchase #5	$50.92	7.540%	$54.7594	$54.76	$54.75	$54.80
Purchase #6	$131.86	4.477%	$137.7634	$137.76	$137.75	$137.80
Purchase #7	$223.87	11.808%	$250.3046	$250.30	$250.30	$250.30
7 purchase totals =	$637.99		$700.1881	$700.19	$700.20	$700.20