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	$229.82	12.662%	$258.9198	$258.92	$258.90	$258.90
Purchase #2	$10.47	4.246%	$10.9146	$10.91	$10.90	$10.90
Purchase #3	$232.81	6.328%	$247.5422	$247.54	$247.55	$247.50
Purchase #4	$197.34	11.661%	$220.3518	$220.35	$220.35	$220.40
Purchase #5	$13.48	9.194%	$14.7194	$14.72	$14.70	$14.70
Purchase #6	$231.72	4.142%	$241.3178	$241.32	$241.30	$241.30
Purchase #7	$64.44	5.270%	$67.836	$67.84	$67.85	$67.80
7 purchase totals =	$980.08		$1,061.6016	$1,061.60	$1,061.55	$1,061.50