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	$168.39	8.233%	$182.2535	$182.25	$182.25	$182.30
Purchase #2	$142.49	12.139%	$159.7869	$159.79	$159.80	$159.80
Purchase #3	$37.59	10.554%	$41.5572	$41.56	$41.55	$41.60
Purchase #4	$214.59	6.697%	$228.9611	$228.96	$228.95	$229.00
Purchase #5	$139.75	11.781%	$156.2139	$156.21	$156.20	$156.20
Purchase #6	$144.76	10.411%	$159.831	$159.83	$159.85	$159.80
Purchase #7	$132.45	9.723%	$145.3281	$145.33	$145.35	$145.30
7 purchase totals =	$980.02		$1,073.9317	$1,073.93	$1,073.95	$1,074.00