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	$131.55	4.150%	$137.0093	$137.01	$137.00	$137.00
Purchase #2	$198.84	5.409%	$209.5953	$209.60	$209.60	$209.60
Purchase #3	$81.37	10.422%	$89.8504	$89.85	$89.85	$89.90
Purchase #4	$172.80	3.301%	$178.5041	$178.50	$178.50	$178.50
Purchase #5	$205.71	6.849%	$219.7991	$219.80	$219.80	$219.80
Purchase #6	$51.36	4.764%	$53.8068	$53.81	$53.80	$53.80
Purchase #7	$167.72	8.668%	$182.258	$182.26	$182.25	$182.30
7 purchase totals =	$1,009.35		$1,070.8230	$1,070.83	$1,070.80	$1,070.90