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	$87.96	5.249%	$92.577	$92.58	$92.60	$92.60
Purchase #2	$98.75	4.465%	$103.1592	$103.16	$103.15	$103.20
Purchase #3	$179.54	11.618%	$200.399	$200.40	$200.40	$200.40
Purchase #4	$40.44	10.548%	$44.7056	$44.71	$44.70	$44.70
Purchase #5	$160.97	13.508%	$182.7138	$182.71	$182.70	$182.70
Purchase #6	$73.61	6.629%	$78.4896	$78.49	$78.50	$78.50
Purchase #7	$99.75	13.716%	$113.4317	$113.43	$113.45	$113.40
7 purchase totals =	$741.02		$815.4759	$815.48	$815.50	$815.50