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	$185.73	12.829%	$209.5573	$209.56	$209.55	$209.60
Purchase #2	$163.94	5.524%	$172.996	$173.00	$173.00	$173.00
Purchase #3	$222.42	5.458%	$234.5597	$234.56	$234.55	$234.60
Purchase #4	$56.93	4.254%	$59.3518	$59.35	$59.35	$59.40
Purchase #5	$163.51	4.845%	$171.4321	$171.43	$171.45	$171.40
Purchase #6	$119.87	13.571%	$136.1376	$136.14	$136.15	$136.10
Purchase #7	$157.52	6.873%	$168.3463	$168.35	$168.35	$168.30
7 purchase totals =	$1,069.92		$1,152.3808	$1,152.39	$1,152.40	$1,152.40