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	$208.66	8.336%	$226.0539	$226.05	$226.05	$226.10
Purchase #2	$79.71	13.808%	$90.7164	$90.72	$90.70	$90.70
Purchase #3	$108.75	11.437%	$121.1877	$121.19	$121.20	$121.20
Purchase #4	$70.31	12.283%	$78.9462	$78.95	$78.95	$78.90
Purchase #5	$96.55	7.428%	$103.7217	$103.72	$103.70	$103.70
Purchase #6	$200.88	5.256%	$211.4383	$211.44	$211.45	$211.40
Purchase #7	$210.47	7.176%	$225.5733	$225.57	$225.55	$225.60
7 purchase totals =	$975.33		$1,057.6375	$1,057.64	$1,057.60	$1,057.60