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	$234.29	10.484%	$258.853	$258.85	$258.85	$258.90
Purchase #2	$184.41	11.364%	$205.3664	$205.37	$205.35	$205.40
Purchase #3	$230.70	5.668%	$243.7761	$243.78	$243.80	$243.80
Purchase #4	$15.59	11.108%	$17.3217	$17.32	$17.30	$17.30
Purchase #5	$71.86	9.829%	$78.9231	$78.92	$78.90	$78.90
Purchase #6	$173.44	4.862%	$181.8727	$181.87	$181.85	$181.90
Purchase #7	$149.78	4.292%	$156.2086	$156.21	$156.20	$156.20
7 purchase totals =	$1,060.07		$1,142.3216	$1,142.32	$1,142.25	$1,142.40