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	$56.37	10.382%	$62.2223	$62.22	$62.20	$62.20
Purchase #2	$34.75	10.332%	$38.3404	$38.34	$38.35	$38.30
Purchase #3	$99.98	11.429%	$111.4067	$111.41	$111.40	$111.40
Purchase #4	$199.80	6.591%	$212.9688	$212.97	$212.95	$213.00
Purchase #5	$52.53	12.619%	$59.1588	$59.16	$59.15	$59.20
Purchase #6	$145.57	9.140%	$158.8751	$158.88	$158.90	$158.90
Purchase #7	$231.57	3.544%	$239.7768	$239.78	$239.80	$239.80
7 purchase totals =	$820.57		$882.7489	$882.76	$882.75	$882.80