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	$181.54	9.331%	$198.4795	$198.48	$198.50	$198.50
Purchase #2	$138.48	7.493%	$148.8563	$148.86	$148.85	$148.90
Purchase #3	$176.64	11.353%	$196.6939	$196.69	$196.70	$196.70
Purchase #4	$85.89	13.304%	$97.3168	$97.32	$97.30	$97.30
Purchase #5	$89.44	9.423%	$97.8679	$97.87	$97.85	$97.90
Purchase #6	$38.97	8.850%	$42.4188	$42.42	$42.40	$42.40
Purchase #7	$44.31	13.452%	$50.2706	$50.27	$50.25	$50.30
7 purchase totals =	$755.27		$831.9038	$831.91	$831.85	$832.00