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	$147.52	11.667%	$164.7312	$164.73	$164.75	$164.70
Purchase #2	$187.93	10.845%	$208.311	$208.31	$208.30	$208.30
Purchase #3	$70.64	7.509%	$75.9444	$75.94	$75.95	$75.90
Purchase #4	$94.62	10.494%	$104.5494	$104.55	$104.55	$104.50
Purchase #5	$72.30	8.508%	$78.4513	$78.45	$78.45	$78.50
Purchase #6	$235.40	11.422%	$262.2874	$262.29	$262.30	$262.30
Purchase #7	$168.33	13.830%	$191.61	$191.61	$191.60	$191.60
7 purchase totals =	$976.74		$1,085.8847	$1,085.88	$1,085.90	$1,085.80