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	$86.76	11.853%	$97.0437	$97.04	$97.05	$97.00
Purchase #2	$108.94	4.326%	$113.6527	$113.65	$113.65	$113.70
Purchase #3	$212.48	4.558%	$222.1648	$222.16	$222.15	$222.20
Purchase #4	$98.82	6.375%	$105.1198	$105.12	$105.10	$105.10
Purchase #5	$131.55	5.847%	$139.2417	$139.24	$139.25	$139.20
Purchase #6	$98.61	13.458%	$111.8809	$111.88	$111.90	$111.90
Purchase #7	$147.91	13.641%	$168.0864	$168.09	$168.10	$168.10
7 purchase totals =	$885.07		$957.1900	$957.18	$957.20	$957.20