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	$154.71	11.676%	$172.7739	$172.77	$172.75	$172.80
Purchase #2	$215.88	8.691%	$234.6421	$234.64	$234.65	$234.60
Purchase #3	$59.98	4.363%	$62.5969	$62.60	$62.60	$62.60
Purchase #4	$175.51	9.793%	$192.6977	$192.70	$192.70	$192.70
Purchase #5	$157.94	12.229%	$177.2545	$177.25	$177.25	$177.30
Purchase #6	$54.59	10.616%	$60.3853	$60.39	$60.40	$60.40
Purchase #7	$186.89	7.224%	$200.3909	$200.39	$200.40	$200.40
7 purchase totals =	$1,005.50		$1,100.7413	$1,100.74	$1,100.75	$1,100.80