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	$173.73	12.823%	$196.0074	$196.01	$196.00	$196.00
Purchase #2	$211.29	4.436%	$220.6628	$220.66	$220.65	$220.70
Purchase #3	$35.33	9.844%	$38.8079	$38.81	$38.80	$38.80
Purchase #4	$108.79	13.447%	$123.419	$123.42	$123.40	$123.40
Purchase #5	$5.44	3.261%	$5.6174	$5.62	$5.60	$5.60
Purchase #6	$73.80	6.697%	$78.7424	$78.74	$78.75	$78.70
Purchase #7	$171.47	12.725%	$193.2896	$193.29	$193.30	$193.30
7 purchase totals =	$779.85		$856.5465	$856.55	$856.50	$856.50