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	$59.77	11.145%	$66.4314	$66.43	$66.45	$66.40
Purchase #2	$69.43	11.264%	$77.2506	$77.25	$77.25	$77.30
Purchase #3	$197.90	7.589%	$212.9186	$212.92	$212.90	$212.90
Purchase #4	$47.89	8.245%	$51.8385	$51.84	$51.85	$51.80
Purchase #5	$149.98	10.193%	$165.2675	$165.27	$165.25	$165.30
Purchase #6	$158.88	9.817%	$174.4772	$174.48	$174.50	$174.50
Purchase #7	$149.39	12.386%	$167.8934	$167.89	$167.90	$167.90
7 purchase totals =	$833.24		$916.0772	$916.08	$916.10	$916.10