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	$249.89	6.221%	$265.4357	$265.44	$265.45	$265.40
Purchase #2	$12.39	7.440%	$13.3118	$13.31	$13.30	$13.30
Purchase #3	$164.56	7.246%	$176.484	$176.48	$176.50	$176.50
Purchase #4	$78.78	11.296%	$87.679	$87.68	$87.70	$87.70
Purchase #5	$71.87	13.408%	$81.5063	$81.51	$81.50	$81.50
Purchase #6	$29.47	10.345%	$32.5187	$32.52	$32.50	$32.50
Purchase #7	$148.89	10.461%	$164.4654	$164.47	$164.45	$164.50
7 purchase totals =	$755.85		$821.4009	$821.41	$821.40	$821.40