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	$157.83	9.598%	$172.9785	$172.98	$173.00	$173.00
Purchase #2	$156.84	12.253%	$176.0576	$176.06	$176.05	$176.10
Purchase #3	$165.52	10.312%	$182.5884	$182.59	$182.60	$182.60
Purchase #4	$85.71	4.509%	$89.5747	$89.57	$89.55	$89.60
Purchase #5	$131.49	4.752%	$137.7384	$137.74	$137.75	$137.70
Purchase #6	$92.38	9.163%	$100.8448	$100.84	$100.85	$100.80
Purchase #7	$39.39	13.208%	$44.5926	$44.59	$44.60	$44.60
7 purchase totals =	$829.16		$904.3750	$904.37	$904.40	$904.40