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	$159.32	5.404%	$167.9297	$167.93	$167.95	$167.90
Purchase #2	$213.48	8.349%	$231.3034	$231.30	$231.30	$231.30
Purchase #3	$180.77	8.489%	$196.1156	$196.12	$196.10	$196.10
Purchase #4	$132.57	7.393%	$142.3709	$142.37	$142.35	$142.40
Purchase #5	$245.89	10.433%	$271.5437	$271.54	$271.55	$271.50
Purchase #6	$23.78	6.757%	$25.3868	$25.39	$25.40	$25.40
Purchase #7	$110.28	4.845%	$115.6231	$115.62	$115.60	$115.60
7 purchase totals =	$1,066.09		$1,150.2732	$1,150.27	$1,150.25	$1,150.20