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	$49.37	9.302%	$53.9624	$53.96	$53.95	$54.00
Purchase #2	$185.49	12.409%	$208.5075	$208.51	$208.50	$208.50
Purchase #3	$196.88	4.439%	$205.6195	$205.62	$205.60	$205.60
Purchase #4	$238.45	3.847%	$247.6232	$247.62	$247.60	$247.60
Purchase #5	$59.67	13.514%	$67.7338	$67.73	$67.75	$67.70
Purchase #6	$98.80	6.287%	$105.0116	$105.01	$105.00	$105.00
Purchase #7	$35.67	4.139%	$37.1464	$37.15	$37.15	$37.10
7 purchase totals =	$864.33		$925.6044	$925.60	$925.55	$925.50