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	$5.47	8.519%	$5.936	$5.94	$5.95	$5.90
Purchase #2	$167.91	6.146%	$178.2297	$178.23	$178.25	$178.20
Purchase #3	$114.58	11.310%	$127.539	$127.54	$127.55	$127.50
Purchase #4	$139.52	3.483%	$144.3795	$144.38	$144.40	$144.40
Purchase #5	$113.78	10.256%	$125.4493	$125.45	$125.45	$125.40
Purchase #6	$188.46	8.806%	$205.0558	$205.06	$205.05	$205.10
Purchase #7	$136.32	10.651%	$150.8394	$150.84	$150.85	$150.80
7 purchase totals =	$866.04		$937.4287	$937.44	$937.50	$937.30