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	$167.71	8.843%	$182.5406	$182.54	$182.55	$182.50
Purchase #2	$210.50	8.313%	$227.9989	$228.00	$228.00	$228.00
Purchase #3	$89.91	11.297%	$100.0671	$100.07	$100.05	$100.10
Purchase #4	$135.98	7.680%	$146.4233	$146.42	$146.40	$146.40
Purchase #5	$225.91	6.405%	$240.3795	$240.38	$240.40	$240.40
Purchase #6	$31.41	3.772%	$32.5948	$32.59	$32.60	$32.60
Purchase #7	$31.59	4.261%	$32.936	$32.94	$32.95	$32.90
7 purchase totals =	$893.01		$962.9402	$962.94	$962.95	$962.90