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	$187.29	5.595%	$197.7689	$197.77	$197.75	$197.80
Purchase #2	$87.83	5.450%	$92.6167	$92.62	$92.60	$92.60
Purchase #3	$72.82	7.556%	$78.3223	$78.32	$78.30	$78.30
Purchase #4	$174.71	11.167%	$194.2199	$194.22	$194.20	$194.20
Purchase #5	$123.66	7.467%	$132.8937	$132.89	$132.90	$132.90
Purchase #6	$20.59	6.222%	$21.8711	$21.87	$21.85	$21.90
Purchase #7	$37.95	7.627%	$40.8444	$40.84	$40.85	$40.80
7 purchase totals =	$704.85		$758.5370	$758.53	$758.45	$758.50