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	$77.35	6.792%	$82.6036	$82.60	$82.60	$82.60
Purchase #2	$72.28	8.439%	$78.3797	$78.38	$78.40	$78.40
Purchase #3	$13.69	4.737%	$14.3385	$14.34	$14.35	$14.30
Purchase #4	$70.70	11.262%	$78.6622	$78.66	$78.65	$78.70
Purchase #5	$173.66	9.835%	$190.7395	$190.74	$190.75	$190.70
Purchase #6	$200.66	6.130%	$212.9605	$212.96	$212.95	$213.00
Purchase #7	$184.44	13.747%	$209.795	$209.80	$209.80	$209.80
7 purchase totals =	$792.78		$867.4790	$867.48	$867.50	$867.50