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	$14.67	12.625%	$16.5221	$16.52	$16.50	$16.50
Purchase #2	$243.61	11.456%	$271.518	$271.52	$271.50	$271.50
Purchase #3	$236.31	5.476%	$249.2503	$249.25	$249.25	$249.30
Purchase #4	$51.29	4.465%	$53.5801	$53.58	$53.60	$53.60
Purchase #5	$9.95	5.394%	$10.4867	$10.49	$10.50	$10.50
Purchase #6	$212.27	12.155%	$238.0714	$238.07	$238.05	$238.10
Purchase #7	$190.61	11.242%	$212.0384	$212.04	$212.05	$212.00
7 purchase totals =	$958.71		$1,051.4670	$1,051.47	$1,051.45	$1,051.50