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	$181.41	3.443%	$187.6559	$187.66	$187.65	$187.70
Purchase #2	$13.31	3.340%	$13.7546	$13.75	$13.75	$13.80
Purchase #3	$198.41	3.161%	$204.6817	$204.68	$204.70	$204.70
Purchase #4	$105.42	12.544%	$118.6439	$118.64	$118.65	$118.60
Purchase #5	$209.82	6.230%	$222.8918	$222.89	$222.90	$222.90
Purchase #6	$106.71	4.407%	$111.4127	$111.41	$111.40	$111.40
Purchase #7	$29.91	4.210%	$31.1692	$31.17	$31.15	$31.20
7 purchase totals =	$844.99		$890.2098	$890.20	$890.20	$890.30