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	$179.92	9.223%	$196.514	$196.51	$196.50	$196.50
Purchase #2	$224.59	6.867%	$240.0126	$240.01	$240.00	$240.00
Purchase #3	$153.93	12.689%	$173.4622	$173.46	$173.45	$173.50
Purchase #4	$153.59	9.827%	$168.6833	$168.68	$168.70	$168.70
Purchase #5	$22.50	12.838%	$25.3886	$25.39	$25.40	$25.40
Purchase #6	$229.51	5.428%	$241.9678	$241.97	$241.95	$242.00
Purchase #7	$103.29	8.346%	$111.9106	$111.91	$111.90	$111.90
7 purchase totals =	$1,067.33		$1,157.9391	$1,157.93	$1,157.90	$1,158.00