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	$78.52	4.476%	$82.0346	$82.03	$82.05	$82.00
Purchase #2	$20.89	6.423%	$22.2318	$22.23	$22.25	$22.20
Purchase #3	$194.85	5.636%	$205.8317	$205.83	$205.85	$205.80
Purchase #4	$82.96	12.499%	$93.3292	$93.33	$93.35	$93.30
Purchase #5	$189.67	13.465%	$215.2091	$215.21	$215.20	$215.20
Purchase #6	$213.53	9.761%	$234.3727	$234.37	$234.35	$234.40
Purchase #7	$224.37	4.106%	$233.5826	$233.58	$233.60	$233.60
7 purchase totals =	$1,004.79		$1,086.5917	$1,086.58	$1,086.65	$1,086.50