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	$235.93	12.639%	$265.7492	$265.75	$265.75	$265.70
Purchase #2	$126.71	13.260%	$143.5117	$143.51	$143.50	$143.50
Purchase #3	$11.62	7.339%	$12.4728	$12.47	$12.45	$12.50
Purchase #4	$159.81	3.118%	$164.7929	$164.79	$164.80	$164.80
Purchase #5	$249.28	12.227%	$279.7595	$279.76	$279.75	$279.80
Purchase #6	$207.55	7.874%	$223.8925	$223.89	$223.90	$223.90
Purchase #7	$100.78	13.554%	$114.4397	$114.44	$114.45	$114.40
7 purchase totals =	$1,091.68		$1,204.6183	$1,204.61	$1,204.60	$1,204.60