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	$197.32	10.706%	$218.4451	$218.45	$218.45	$218.40
Purchase #2	$206.43	11.857%	$230.9064	$230.91	$230.90	$230.90
Purchase #3	$54.73	8.350%	$59.3	$59.30	$59.30	$59.30
Purchase #4	$36.46	8.595%	$39.5937	$39.59	$39.60	$39.60
Purchase #5	$39.28	6.222%	$41.724	$41.72	$41.70	$41.70
Purchase #6	$117.81	7.806%	$127.0062	$127.01	$127.00	$127.00
Purchase #7	$26.53	8.713%	$28.8416	$28.84	$28.85	$28.80
7 purchase totals =	$678.56		$745.8170	$745.82	$745.80	$745.70