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	$168.36	9.217%	$183.8777	$183.88	$183.90	$183.90
Purchase #2	$50.68	11.785%	$56.6526	$56.65	$56.65	$56.70
Purchase #3	$235.68	4.195%	$245.5668	$245.57	$245.55	$245.60
Purchase #4	$139.36	9.241%	$152.2383	$152.24	$152.25	$152.20
Purchase #5	$40.42	6.299%	$42.9661	$42.97	$42.95	$43.00
Purchase #6	$173.39	8.776%	$188.6067	$188.61	$188.60	$188.60
Purchase #7	$196.50	9.757%	$215.6725	$215.67	$215.65	$215.70
7 purchase totals =	$1,004.39		$1,085.5807	$1,085.59	$1,085.55	$1,085.70