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	$237.82	11.809%	$265.9042	$265.90	$265.90	$265.90
Purchase #2	$163.88	3.496%	$169.6092	$169.61	$169.60	$169.60
Purchase #3	$139.30	4.648%	$145.7747	$145.77	$145.75	$145.80
Purchase #4	$89.76	6.353%	$95.4625	$95.46	$95.45	$95.50
Purchase #5	$192.67	11.210%	$214.2683	$214.27	$214.25	$214.30
Purchase #6	$9.95	3.494%	$10.2977	$10.30	$10.30	$10.30
Purchase #7	$92.56	13.768%	$105.3037	$105.30	$105.30	$105.30
7 purchase totals =	$925.94		$1,006.6203	$1,006.61	$1,006.55	$1,006.70