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	$180.25	3.662%	$186.8508	$186.85	$186.85	$186.90
Purchase #2	$111.52	5.346%	$117.4819	$117.48	$117.50	$117.50
Purchase #3	$103.61	3.580%	$107.3192	$107.32	$107.30	$107.30
Purchase #4	$104.46	4.274%	$108.9246	$108.92	$108.90	$108.90
Purchase #5	$36.96	7.266%	$39.6455	$39.65	$39.65	$39.60
Purchase #6	$156.39	5.357%	$164.7678	$164.77	$164.75	$164.80
Purchase #7	$216.92	5.820%	$229.5447	$229.54	$229.55	$229.50
7 purchase totals =	$910.11		$954.5345	$954.53	$954.50	$954.50