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	$164.75	10.259%	$181.6517	$181.65	$181.65	$181.70
Purchase #2	$209.93	7.389%	$225.4417	$225.44	$225.45	$225.40
Purchase #3	$189.62	10.368%	$209.2798	$209.28	$209.30	$209.30
Purchase #4	$40.52	7.253%	$43.4589	$43.46	$43.45	$43.50
Purchase #5	$12.30	10.504%	$13.592	$13.59	$13.60	$13.60
Purchase #6	$87.83	4.325%	$91.6286	$91.63	$91.65	$91.60
Purchase #7	$160.90	9.704%	$176.5137	$176.51	$176.50	$176.50
7 purchase totals =	$865.85		$941.5664	$941.56	$941.60	$941.60