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	$147.25	12.389%	$165.4928	$165.49	$165.50	$165.50
Purchase #2	$78.98	11.206%	$87.8305	$87.83	$87.85	$87.80
Purchase #3	$115.61	7.338%	$124.0935	$124.09	$124.10	$124.10
Purchase #4	$148.75	4.517%	$155.469	$155.47	$155.45	$155.50
Purchase #5	$250.84	7.617%	$269.9465	$269.95	$269.95	$269.90
Purchase #6	$49.31	5.693%	$52.1172	$52.12	$52.10	$52.10
Purchase #7	$142.78	4.665%	$149.4407	$149.44	$149.45	$149.40
7 purchase totals =	$933.52		$1,004.3902	$1,004.39	$1,004.40	$1,004.30