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	$228.92	9.272%	$250.1455	$250.15	$250.15	$250.10
Purchase #2	$10.50	7.114%	$11.247	$11.25	$11.25	$11.20
Purchase #3	$87.51	12.571%	$98.5109	$98.51	$98.50	$98.50
Purchase #4	$50.31	6.261%	$53.4599	$53.46	$53.45	$53.50
Purchase #5	$87.77	11.225%	$97.6222	$97.62	$97.60	$97.60
Purchase #6	$161.93	7.846%	$174.635	$174.64	$174.65	$174.60
Purchase #7	$24.96	12.552%	$28.093	$28.09	$28.10	$28.10
7 purchase totals =	$651.90		$713.7135	$713.72	$713.70	$713.60