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	$235.92	12.217%	$264.7423	$264.74	$264.75	$264.70
Purchase #2	$181.55	8.260%	$196.546	$196.55	$196.55	$196.50
Purchase #3	$158.84	12.120%	$178.0914	$178.09	$178.10	$178.10
Purchase #4	$167.38	3.542%	$173.3086	$173.31	$173.30	$173.30
Purchase #5	$101.81	3.146%	$105.0129	$105.01	$105.00	$105.00
Purchase #6	$136.61	10.625%	$151.1248	$151.12	$151.10	$151.10
Purchase #7	$101.70	11.683%	$113.5816	$113.58	$113.60	$113.60
7 purchase totals =	$1,083.81		$1,182.4076	$1,182.40	$1,182.40	$1,182.30