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	$40.51	7.720%	$43.6374	$43.64	$43.65	$43.60
Purchase #2	$82.38	3.464%	$85.2336	$85.23	$85.25	$85.20
Purchase #3	$152.93	6.270%	$162.5187	$162.52	$162.50	$162.50
Purchase #4	$128.77	8.261%	$139.4077	$139.41	$139.40	$139.40
Purchase #5	$152.34	13.556%	$172.9912	$172.99	$173.00	$173.00
Purchase #6	$231.85	8.420%	$251.3718	$251.37	$251.35	$251.40
Purchase #7	$161.48	11.372%	$179.8435	$179.84	$179.85	$179.80
7 purchase totals =	$950.26		$1,035.0039	$1,035.00	$1,035.00	$1,034.90