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	$56.44	5.628%	$59.6164	$59.62	$59.60	$59.60
Purchase #2	$239.60	8.122%	$259.0603	$259.06	$259.05	$259.10
Purchase #3	$184.73	7.605%	$198.7787	$198.78	$198.80	$198.80
Purchase #4	$99.92	5.660%	$105.5755	$105.58	$105.60	$105.60
Purchase #5	$111.26	8.612%	$120.8417	$120.84	$120.85	$120.80
Purchase #6	$135.43	11.799%	$151.4094	$151.41	$151.40	$151.40
Purchase #7	$224.40	10.817%	$248.6733	$248.67	$248.65	$248.70
7 purchase totals =	$1,051.78		$1,143.9553	$1,143.96	$1,143.95	$1,144.00