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	$65.39	13.161%	$73.996	$74.00	$74.00	$74.00
Purchase #2	$89.59	12.163%	$100.4868	$100.49	$100.50	$100.50
Purchase #3	$72.55	9.334%	$79.3218	$79.32	$79.30	$79.30
Purchase #4	$22.85	3.437%	$23.6354	$23.64	$23.65	$23.60
Purchase #5	$229.58	11.109%	$255.084	$255.08	$255.10	$255.10
Purchase #6	$225.88	12.409%	$253.9094	$253.91	$253.90	$253.90
Purchase #7	$236.93	8.269%	$256.5217	$256.52	$256.50	$256.50
7 purchase totals =	$942.77		$1,042.9551	$1,042.96	$1,042.95	$1,042.90