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	$143.94	8.279%	$155.8568	$155.86	$155.85	$155.90
Purchase #2	$47.59	10.677%	$52.6712	$52.67	$52.65	$52.70
Purchase #3	$13.67	9.797%	$15.0092	$15.01	$15.00	$15.00
Purchase #4	$199.84	8.712%	$217.2501	$217.25	$217.25	$217.30
Purchase #5	$31.91	4.846%	$33.4564	$33.46	$33.45	$33.50
Purchase #6	$189.31	10.848%	$209.8463	$209.85	$209.85	$209.80
Purchase #7	$34.55	11.314%	$38.459	$38.46	$38.45	$38.50
7 purchase totals =	$660.81		$722.5490	$722.56	$722.50	$722.70