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	$78.41	10.261%	$86.4557	$86.46	$86.45	$86.50
Purchase #2	$144.42	7.291%	$154.9497	$154.95	$154.95	$154.90
Purchase #3	$85.80	3.787%	$89.0492	$89.05	$89.05	$89.00
Purchase #4	$222.74	12.850%	$251.3621	$251.36	$251.35	$251.40
Purchase #5	$155.77	13.528%	$176.8426	$176.84	$176.85	$176.80
Purchase #6	$172.48	8.297%	$186.7907	$186.79	$186.80	$186.80
Purchase #7	$112.79	6.803%	$120.4631	$120.46	$120.45	$120.50
7 purchase totals =	$972.41		$1,065.9131	$1,065.91	$1,065.90	$1,065.90