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	$241.66	9.587%	$264.8279	$264.83	$264.85	$264.80
Purchase #2	$76.90	10.572%	$85.0299	$85.03	$85.05	$85.00
Purchase #3	$149.95	10.188%	$165.2269	$165.23	$165.25	$165.20
Purchase #4	$196.96	9.392%	$215.4585	$215.46	$215.45	$215.50
Purchase #5	$122.58	8.304%	$132.759	$132.76	$132.75	$132.80
Purchase #6	$220.36	12.546%	$248.0064	$248.01	$248.00	$248.00
Purchase #7	$142.47	12.699%	$160.5623	$160.56	$160.55	$160.60
7 purchase totals =	$1,150.88		$1,271.8709	$1,271.88	$1,271.90	$1,271.90