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	$39.43	4.710%	$41.2872	$41.29	$41.30	$41.30
Purchase #2	$50.67	3.613%	$52.5007	$52.50	$52.50	$52.50
Purchase #3	$233.53	9.510%	$255.7387	$255.74	$255.75	$255.70
Purchase #4	$199.96	12.493%	$224.941	$224.94	$224.95	$224.90
Purchase #5	$18.46	8.808%	$20.086	$20.09	$20.10	$20.10
Purchase #6	$107.62	6.742%	$114.8757	$114.88	$114.90	$114.90
Purchase #7	$89.57	9.722%	$98.278	$98.28	$98.30	$98.30
7 purchase totals =	$739.24		$807.7073	$807.72	$807.80	$807.70