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	$175.26	7.517%	$188.4343	$188.43	$188.45	$188.40
Purchase #2	$145.31	6.552%	$154.8307	$154.83	$154.85	$154.80
Purchase #3	$122.60	13.815%	$139.5372	$139.54	$139.55	$139.50
Purchase #4	$104.61	7.414%	$112.3658	$112.37	$112.35	$112.40
Purchase #5	$172.95	7.539%	$185.9887	$185.99	$186.00	$186.00
Purchase #6	$33.64	11.492%	$37.5059	$37.51	$37.50	$37.50
Purchase #7	$46.42	3.417%	$48.0062	$48.01	$48.00	$48.00
7 purchase totals =	$800.79		$866.6688	$866.68	$866.70	$866.60