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	$38.85	5.120%	$40.8391	$40.84	$40.85	$40.80
Purchase #2	$21.38	3.607%	$22.1512	$22.15	$22.15	$22.20
Purchase #3	$222.43	11.534%	$248.0851	$248.09	$248.10	$248.10
Purchase #4	$60.88	6.456%	$64.8104	$64.81	$64.80	$64.80
Purchase #5	$114.41	12.290%	$128.471	$128.47	$128.45	$128.50
Purchase #6	$222.96	5.648%	$235.5528	$235.55	$235.55	$235.60
Purchase #7	$245.70	12.533%	$276.4936	$276.49	$276.50	$276.50
7 purchase totals =	$926.61		$1,016.4032	$1,016.40	$1,016.40	$1,016.50