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	$116.63	9.256%	$127.4253	$127.43	$127.45	$127.40
Purchase #2	$132.27	5.617%	$139.6996	$139.70	$139.70	$139.70
Purchase #3	$153.37	11.793%	$171.4569	$171.46	$171.45	$171.50
Purchase #4	$39.77	3.268%	$41.0697	$41.07	$41.05	$41.10
Purchase #5	$104.96	3.539%	$108.6745	$108.67	$108.65	$108.70
Purchase #6	$185.85	4.423%	$194.0701	$194.07	$194.05	$194.10
Purchase #7	$18.99	8.282%	$20.5628	$20.56	$20.55	$20.60
7 purchase totals =	$751.84		$802.9589	$802.96	$802.90	$803.10