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	$109.85	3.156%	$113.3169	$113.32	$113.30	$113.30
Purchase #2	$132.81	13.493%	$150.7301	$150.73	$150.75	$150.70
Purchase #3	$221.68	12.271%	$248.8824	$248.88	$248.90	$248.90
Purchase #4	$142.30	10.269%	$156.9128	$156.91	$156.90	$156.90
Purchase #5	$31.62	13.159%	$35.7809	$35.78	$35.80	$35.80
Purchase #6	$95.55	4.684%	$100.0256	$100.03	$100.05	$100.00
Purchase #7	$225.37	5.210%	$237.1118	$237.11	$237.10	$237.10
7 purchase totals =	$959.18		$1,042.7605	$1,042.76	$1,042.80	$1,042.70