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	$195.76	12.157%	$219.5585	$219.56	$219.55	$219.60
Purchase #2	$25.70	10.142%	$28.3065	$28.31	$28.30	$28.30
Purchase #3	$184.28	11.551%	$205.5662	$205.57	$205.55	$205.60
Purchase #4	$247.30	7.372%	$265.531	$265.53	$265.55	$265.50
Purchase #5	$119.94	7.104%	$128.4605	$128.46	$128.45	$128.50
Purchase #6	$148.80	10.852%	$164.9478	$164.95	$164.95	$164.90
Purchase #7	$149.71	11.493%	$166.9162	$166.92	$166.90	$166.90
7 purchase totals =	$1,071.49		$1,179.2867	$1,179.30	$1,179.25	$1,179.30