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	$169.98	7.697%	$183.0634	$183.06	$183.05	$183.10
Purchase #2	$128.54	7.362%	$138.0031	$138.00	$138.00	$138.00
Purchase #3	$208.74	3.416%	$215.8706	$215.87	$215.85	$215.90
Purchase #4	$90.39	10.519%	$99.8981	$99.90	$99.90	$99.90
Purchase #5	$10.66	7.669%	$11.4775	$11.48	$11.50	$11.50
Purchase #6	$67.27	7.302%	$72.1821	$72.18	$72.20	$72.20
Purchase #7	$49.46	10.399%	$54.6033	$54.60	$54.60	$54.60
7 purchase totals =	$725.04		$775.0981	$775.09	$775.10	$775.20