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	$178.42	5.798%	$188.7648	$188.76	$188.75	$188.80
Purchase #2	$167.90	12.491%	$188.8724	$188.87	$188.85	$188.90
Purchase #3	$36.96	12.281%	$41.4991	$41.50	$41.50	$41.50
Purchase #4	$46.82	10.818%	$51.885	$51.89	$51.90	$51.90
Purchase #5	$147.60	9.673%	$161.8773	$161.88	$161.90	$161.90
Purchase #6	$179.80	6.105%	$190.7768	$190.78	$190.80	$190.80
Purchase #7	$181.44	3.599%	$187.97	$187.97	$187.95	$188.00
7 purchase totals =	$938.94		$1,011.6454	$1,011.65	$1,011.65	$1,011.80