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	$75.78	13.706%	$86.1664	$86.17	$86.15	$86.20
Purchase #2	$35.96	3.380%	$37.1754	$37.18	$37.20	$37.20
Purchase #3	$178.45	3.823%	$185.2721	$185.27	$185.25	$185.30
Purchase #4	$136.35	10.390%	$150.5168	$150.52	$150.50	$150.50
Purchase #5	$144.33	13.142%	$163.2978	$163.30	$163.30	$163.30
Purchase #6	$226.41	12.668%	$255.0916	$255.09	$255.10	$255.10
Purchase #7	$131.95	4.681%	$138.1266	$138.13	$138.15	$138.10
7 purchase totals =	$929.23		$1,015.6467	$1,015.66	$1,015.65	$1,015.70