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	$168.27	4.596%	$176.0037	$176.00	$176.00	$176.00
Purchase #2	$33.50	11.792%	$37.4503	$37.45	$37.45	$37.50
Purchase #3	$219.35	4.539%	$229.3063	$229.31	$229.30	$229.30
Purchase #4	$94.42	11.146%	$104.9441	$104.94	$104.95	$104.90
Purchase #5	$17.53	11.326%	$19.5154	$19.52	$19.50	$19.50
Purchase #6	$210.44	10.870%	$233.3148	$233.31	$233.30	$233.30
Purchase #7	$151.96	6.189%	$161.3648	$161.36	$161.35	$161.40
7 purchase totals =	$895.47		$961.8994	$961.89	$961.85	$961.90