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	$210.39	5.570%	$222.1087	$222.11	$222.10	$222.10
Purchase #2	$156.74	6.843%	$167.4657	$167.47	$167.45	$167.50
Purchase #3	$96.40	6.871%	$103.0236	$103.02	$103.00	$103.00
Purchase #4	$108.86	6.500%	$115.9359	$115.94	$115.95	$115.90
Purchase #5	$224.77	12.497%	$252.8595	$252.86	$252.85	$252.90
Purchase #6	$30.49	4.610%	$31.8956	$31.90	$31.90	$31.90
Purchase #7	$75.32	9.698%	$82.6245	$82.62	$82.60	$82.60
7 purchase totals =	$902.97		$975.9135	$975.92	$975.85	$975.90