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	$129.72	11.426%	$144.5418	$144.54	$144.55	$144.50
Purchase #2	$129.91	9.677%	$142.4814	$142.48	$142.50	$142.50
Purchase #3	$249.49	6.202%	$264.9634	$264.96	$264.95	$265.00
Purchase #4	$68.59	10.640%	$75.888	$75.89	$75.90	$75.90
Purchase #5	$132.35	13.487%	$150.2	$150.20	$150.20	$150.20
Purchase #6	$41.79	7.375%	$44.872	$44.87	$44.85	$44.90
Purchase #7	$241.42	12.615%	$271.8751	$271.88	$271.90	$271.90
7 purchase totals =	$993.27		$1,094.8217	$1,094.82	$1,094.85	$1,094.90