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	$238.66	6.458%	$254.0727	$254.07	$254.05	$254.10
Purchase #2	$175.71	11.746%	$196.3489	$196.35	$196.35	$196.30
Purchase #3	$170.42	11.496%	$190.0115	$190.01	$190.00	$190.00
Purchase #4	$42.79	12.561%	$48.1649	$48.16	$48.15	$48.20
Purchase #5	$210.57	4.862%	$220.8079	$220.81	$220.80	$220.80
Purchase #6	$89.38	5.619%	$94.4023	$94.40	$94.40	$94.40
Purchase #7	$19.93	9.346%	$21.7927	$21.79	$21.80	$21.80
7 purchase totals =	$947.46		$1,025.6009	$1,025.59	$1,025.55	$1,025.60