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	$249.30	4.725%	$261.0794	$261.08	$261.10	$261.10
Purchase #2	$175.27	13.780%	$199.4222	$199.42	$199.40	$199.40
Purchase #3	$150.37	5.542%	$158.7035	$158.70	$158.70	$158.70
Purchase #4	$172.68	13.512%	$196.0125	$196.01	$196.00	$196.00
Purchase #5	$205.81	9.782%	$225.9423	$225.94	$225.95	$225.90
Purchase #6	$165.50	9.579%	$181.3532	$181.35	$181.35	$181.40
Purchase #7	$171.37	4.468%	$179.0268	$179.03	$179.05	$179.00
7 purchase totals =	$1,290.30		$1,401.5399	$1,401.53	$1,401.55	$1,401.50