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	$228.96	8.711%	$248.9047	$248.90	$248.90	$248.90
Purchase #2	$237.47	4.407%	$247.9353	$247.94	$247.95	$247.90
Purchase #3	$107.89	9.655%	$118.3068	$118.31	$118.30	$118.30
Purchase #4	$139.56	13.482%	$158.3755	$158.38	$158.40	$158.40
Purchase #5	$12.64	9.725%	$13.8692	$13.87	$13.85	$13.90
Purchase #6	$186.71	5.229%	$196.4731	$196.47	$196.45	$196.50
Purchase #7	$51.50	12.147%	$57.7557	$57.76	$57.75	$57.80
7 purchase totals =	$964.73		$1,041.6203	$1,041.63	$1,041.60	$1,041.70