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	$45.62	9.204%	$49.8189	$49.82	$49.80	$49.80
Purchase #2	$119.61	6.175%	$126.9959	$127.00	$127.00	$127.00
Purchase #3	$107.70	5.639%	$113.7732	$113.77	$113.75	$113.80
Purchase #4	$155.54	8.330%	$168.4965	$168.50	$168.50	$168.50
Purchase #5	$141.78	10.427%	$156.5634	$156.56	$156.55	$156.60
Purchase #6	$182.49	5.426%	$192.3919	$192.39	$192.40	$192.40
Purchase #7	$53.58	11.752%	$59.8767	$59.88	$59.90	$59.90
7 purchase totals =	$806.32		$867.9165	$867.92	$867.90	$868.00