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	$37.39	10.188%	$41.1993	$41.20	$41.20	$41.20
Purchase #2	$215.93	6.488%	$229.9395	$229.94	$229.95	$229.90
Purchase #3	$183.47	8.210%	$198.5329	$198.53	$198.55	$198.50
Purchase #4	$196.94	6.374%	$209.493	$209.49	$209.50	$209.50
Purchase #5	$244.67	9.329%	$267.4953	$267.50	$267.50	$267.50
Purchase #6	$104.80	4.485%	$109.5003	$109.50	$109.50	$109.50
Purchase #7	$20.98	4.102%	$21.8406	$21.84	$21.85	$21.80
7 purchase totals =	$1,004.18		$1,078.0009	$1,078.00	$1,078.05	$1,077.90