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	$231.95	11.565%	$258.775	$258.78	$258.80	$258.80
Purchase #2	$159.33	6.600%	$169.8458	$169.85	$169.85	$169.80
Purchase #3	$17.50	4.163%	$18.2285	$18.23	$18.25	$18.20
Purchase #4	$201.76	10.835%	$223.6207	$223.62	$223.60	$223.60
Purchase #5	$226.67	10.180%	$249.745	$249.75	$249.75	$249.70
Purchase #6	$81.40	5.279%	$85.6971	$85.70	$85.70	$85.70
Purchase #7	$40.51	3.405%	$41.8894	$41.89	$41.90	$41.90
7 purchase totals =	$959.12		$1,047.8015	$1,047.82	$1,047.85	$1,047.70