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	$241.27	3.593%	$249.9388	$249.94	$249.95	$249.90
Purchase #2	$206.83	4.726%	$216.6048	$216.60	$216.60	$216.60
Purchase #3	$136.64	11.470%	$152.3126	$152.31	$152.30	$152.30
Purchase #4	$173.96	12.660%	$195.9833	$195.98	$196.00	$196.00
Purchase #5	$194.85	9.779%	$213.9044	$213.90	$213.90	$213.90
Purchase #6	$248.42	10.506%	$274.519	$274.52	$274.50	$274.50
Purchase #7	$137.90	3.848%	$143.2064	$143.21	$143.20	$143.20
7 purchase totals =	$1,339.87		$1,446.4693	$1,446.46	$1,446.45	$1,446.40