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	$184.77	8.287%	$200.0819	$200.08	$200.10	$200.10
Purchase #2	$233.87	12.158%	$262.3039	$262.30	$262.30	$262.30
Purchase #3	$53.54	3.514%	$55.4214	$55.42	$55.40	$55.40
Purchase #4	$41.54	4.787%	$43.5285	$43.53	$43.55	$43.50
Purchase #5	$70.28	4.472%	$73.4229	$73.42	$73.40	$73.40
Purchase #6	$31.98	13.869%	$36.4153	$36.42	$36.40	$36.40
Purchase #7	$178.42	11.145%	$198.3049	$198.30	$198.30	$198.30
7 purchase totals =	$794.40		$869.4788	$869.47	$869.45	$869.40