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	$134.82	5.196%	$141.8252	$141.83	$141.85	$141.80
Purchase #2	$124.39	3.586%	$128.8506	$128.85	$128.85	$128.90
Purchase #3	$200.85	4.274%	$209.4343	$209.43	$209.45	$209.40
Purchase #4	$148.61	3.298%	$153.5112	$153.51	$153.50	$153.50
Purchase #5	$80.29	9.346%	$87.7939	$87.79	$87.80	$87.80
Purchase #6	$47.38	5.848%	$50.1508	$50.15	$50.15	$50.20
Purchase #7	$155.67	11.692%	$173.8709	$173.87	$173.85	$173.90
7 purchase totals =	$892.01		$945.4369	$945.43	$945.45	$945.50