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	$95.65	12.614%	$107.7153	$107.72	$107.70	$107.70
Purchase #2	$94.44	6.728%	$100.7939	$100.79	$100.80	$100.80
Purchase #3	$134.82	11.400%	$150.1895	$150.19	$150.20	$150.20
Purchase #4	$81.83	7.569%	$88.0237	$88.02	$88.00	$88.00
Purchase #5	$120.77	5.791%	$127.7638	$127.76	$127.75	$127.80
Purchase #6	$141.35	7.215%	$151.5484	$151.55	$151.55	$151.50
Purchase #7	$34.64	13.773%	$39.411	$39.41	$39.40	$39.40
7 purchase totals =	$703.50		$765.4456	$765.44	$765.40	$765.40