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	$12.37	5.645%	$13.0683	$13.07	$13.05	$13.10
Purchase #2	$182.68	12.717%	$205.9114	$205.91	$205.90	$205.90
Purchase #3	$62.59	3.237%	$64.616	$64.62	$64.60	$64.60
Purchase #4	$164.41	4.437%	$171.7049	$171.70	$171.70	$171.70
Purchase #5	$199.83	13.873%	$227.5524	$227.55	$227.55	$227.60
Purchase #6	$234.95	9.344%	$256.9037	$256.90	$256.90	$256.90
Purchase #7	$111.89	8.666%	$121.5864	$121.59	$121.60	$121.60
7 purchase totals =	$968.72		$1,061.3431	$1,061.34	$1,061.30	$1,061.40