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	$71.32	10.197%	$78.5925	$78.59	$78.60	$78.60
Purchase #2	$215.89	4.260%	$225.0869	$225.09	$225.10	$225.10
Purchase #3	$160.83	13.211%	$182.0773	$182.08	$182.10	$182.10
Purchase #4	$73.38	3.797%	$76.1662	$76.17	$76.15	$76.20
Purchase #5	$170.29	9.308%	$186.1406	$186.14	$186.15	$186.10
Purchase #6	$84.69	9.677%	$92.8855	$92.89	$92.90	$92.90
Purchase #7	$116.30	8.555%	$126.2495	$126.25	$126.25	$126.20
7 purchase totals =	$892.70		$967.1985	$967.21	$967.25	$967.20