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	$139.69	7.659%	$150.3889	$150.39	$150.40	$150.40
Purchase #2	$92.94	13.815%	$105.7797	$105.78	$105.80	$105.80
Purchase #3	$203.77	9.377%	$222.8775	$222.88	$222.90	$222.90
Purchase #4	$118.25	11.349%	$131.6702	$131.67	$131.65	$131.70
Purchase #5	$30.58	13.210%	$34.6196	$34.62	$34.60	$34.60
Purchase #6	$79.25	3.139%	$81.7377	$81.74	$81.75	$81.70
Purchase #7	$156.72	6.850%	$167.4553	$167.46	$167.45	$167.50
7 purchase totals =	$821.20		$894.5289	$894.54	$894.55	$894.60