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	$233.32	4.166%	$243.0401	$243.04	$243.05	$243.00
Purchase #2	$88.83	13.533%	$100.8514	$100.85	$100.85	$100.90
Purchase #3	$31.35	3.668%	$32.4999	$32.50	$32.50	$32.50
Purchase #4	$156.62	11.626%	$174.8286	$174.83	$174.85	$174.80
Purchase #5	$107.25	5.835%	$113.508	$113.51	$113.50	$113.50
Purchase #6	$41.52	6.161%	$44.078	$44.08	$44.10	$44.10
Purchase #7	$32.79	11.145%	$36.4444	$36.44	$36.45	$36.40
7 purchase totals =	$691.68		$745.2504	$745.25	$745.30	$745.20