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	$82.30	12.225%	$92.3612	$92.36	$92.35	$92.40
Purchase #2	$20.82	5.320%	$21.9276	$21.93	$21.95	$21.90
Purchase #3	$35.93	8.417%	$38.9542	$38.95	$38.95	$39.00
Purchase #4	$44.74	8.237%	$48.4252	$48.43	$48.45	$48.40
Purchase #5	$132.73	11.716%	$148.2806	$148.28	$148.30	$148.30
Purchase #6	$41.95	4.199%	$43.7115	$43.71	$43.70	$43.70
Purchase #7	$57.48	4.228%	$59.9103	$59.91	$59.90	$59.90
7 purchase totals =	$415.95		$453.5706	$453.57	$453.60	$453.60