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	$145.65	11.544%	$162.4638	$162.46	$162.45	$162.50
Purchase #2	$131.55	12.307%	$147.7399	$147.74	$147.75	$147.70
Purchase #3	$129.49	10.835%	$143.5202	$143.52	$143.50	$143.50
Purchase #4	$232.31	7.873%	$250.5998	$250.60	$250.60	$250.60
Purchase #5	$136.94	5.509%	$144.484	$144.48	$144.50	$144.50
Purchase #6	$152.44	5.578%	$160.9431	$160.94	$160.95	$160.90
Purchase #7	$128.70	9.511%	$140.9407	$140.94	$140.95	$140.90
7 purchase totals =	$1,057.08		$1,150.6915	$1,150.68	$1,150.70	$1,150.60