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	$100.96	6.440%	$107.4618	$107.46	$107.45	$107.50
Purchase #2	$86.76	11.336%	$96.5951	$96.60	$96.60	$96.60
Purchase #3	$100.34	11.188%	$111.566	$111.57	$111.55	$111.60
Purchase #4	$170.89	7.314%	$183.3889	$183.39	$183.40	$183.40
Purchase #5	$16.93	10.301%	$18.674	$18.67	$18.65	$18.70
Purchase #6	$149.37	13.198%	$169.0839	$169.08	$169.10	$169.10
Purchase #7	$127.44	8.323%	$138.0468	$138.05	$138.05	$138.00
7 purchase totals =	$752.69		$824.8165	$824.82	$824.80	$824.90