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	$201.85	13.753%	$229.6104	$229.61	$229.60	$229.60
Purchase #2	$44.55	13.343%	$50.4943	$50.49	$50.50	$50.50
Purchase #3	$239.27	6.654%	$255.191	$255.19	$255.20	$255.20
Purchase #4	$249.90	3.235%	$257.9843	$257.98	$258.00	$258.00
Purchase #5	$90.63	4.263%	$94.4936	$94.49	$94.50	$94.50
Purchase #6	$77.31	11.559%	$86.2463	$86.25	$86.25	$86.20
Purchase #7	$118.99	3.377%	$123.0083	$123.01	$123.00	$123.00
7 purchase totals =	$1,022.50		$1,097.0282	$1,097.02	$1,097.05	$1,097.00