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	$214.66	4.293%	$223.8754	$223.88	$223.90	$223.90
Purchase #2	$131.33	11.820%	$146.8532	$146.85	$146.85	$146.90
Purchase #3	$21.99	7.838%	$23.7136	$23.71	$23.70	$23.70
Purchase #4	$106.61	9.530%	$116.7699	$116.77	$116.75	$116.80
Purchase #5	$53.69	11.595%	$59.9154	$59.92	$59.90	$59.90
Purchase #6	$162.35	7.452%	$174.4483	$174.45	$174.45	$174.40
Purchase #7	$70.64	11.160%	$78.5234	$78.52	$78.50	$78.50
7 purchase totals =	$761.27		$824.0992	$824.10	$824.05	$824.10