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	$240.25	6.800%	$256.587	$256.59	$256.60	$256.60
Purchase #2	$146.48	5.114%	$153.971	$153.97	$153.95	$154.00
Purchase #3	$242.89	13.742%	$276.2679	$276.27	$276.25	$276.30
Purchase #4	$101.36	13.290%	$114.8307	$114.83	$114.85	$114.80
Purchase #5	$100.38	10.358%	$110.7774	$110.78	$110.80	$110.80
Purchase #6	$71.72	4.658%	$75.0607	$75.06	$75.05	$75.10
Purchase #7	$47.51	7.197%	$50.9293	$50.93	$50.95	$50.90
7 purchase totals =	$950.59		$1,038.4240	$1,038.43	$1,038.45	$1,038.50