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	$203.80	9.665%	$223.4973	$223.50	$223.50	$223.50
Purchase #2	$242.99	5.152%	$255.5088	$255.51	$255.50	$255.50
Purchase #3	$104.52	3.518%	$108.197	$108.20	$108.20	$108.20
Purchase #4	$230.80	4.483%	$241.1468	$241.15	$241.15	$241.10
Purchase #5	$173.56	6.670%	$185.1365	$185.14	$185.15	$185.10
Purchase #6	$224.93	9.700%	$246.7482	$246.75	$246.75	$246.70
Purchase #7	$155.98	4.271%	$162.6419	$162.64	$162.65	$162.60
7 purchase totals =	$1,336.58		$1,422.8765	$1,422.89	$1,422.90	$1,422.70