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	$151.61	9.513%	$166.0327	$166.03	$166.05	$166.00
Purchase #2	$128.71	10.485%	$142.2052	$142.21	$142.20	$142.20
Purchase #3	$74.33	11.412%	$82.8125	$82.81	$82.80	$82.80
Purchase #4	$7.96	10.272%	$8.7777	$8.78	$8.80	$8.80
Purchase #5	$40.64	4.778%	$42.5818	$42.58	$42.60	$42.60
Purchase #6	$106.99	4.184%	$111.4665	$111.47	$111.45	$111.50
Purchase #7	$94.44	6.511%	$100.589	$100.59	$100.60	$100.60
7 purchase totals =	$604.68		$654.4654	$654.47	$654.50	$654.50