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	$86.78	4.786%	$90.9333	$90.93	$90.95	$90.90
Purchase #2	$165.54	12.338%	$185.9643	$185.96	$185.95	$186.00
Purchase #3	$96.80	5.413%	$102.0398	$102.04	$102.05	$102.00
Purchase #4	$31.37	7.706%	$33.7874	$33.79	$33.80	$33.80
Purchase #5	$200.51	4.699%	$209.932	$209.93	$209.95	$209.90
Purchase #6	$126.67	10.240%	$139.641	$139.64	$139.65	$139.60
Purchase #7	$111.26	4.667%	$116.4525	$116.45	$116.45	$116.50
7 purchase totals =	$818.93		$878.7503	$878.74	$878.80	$878.70