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	$208.57	7.487%	$224.1856	$224.19	$224.20	$224.20
Purchase #2	$113.70	8.624%	$123.5055	$123.51	$123.50	$123.50
Purchase #3	$82.57	4.666%	$86.4227	$86.42	$86.40	$86.40
Purchase #4	$164.39	11.426%	$183.1732	$183.17	$183.15	$183.20
Purchase #5	$116.81	7.102%	$125.1058	$125.11	$125.10	$125.10
Purchase #6	$164.40	12.239%	$184.5209	$184.52	$184.50	$184.50
Purchase #7	$166.46	3.252%	$171.8733	$171.87	$171.85	$171.90
7 purchase totals =	$1,016.90		$1,098.7870	$1,098.79	$1,098.70	$1,098.80