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	$70.92	10.153%	$78.1205	$78.12	$78.10	$78.10
Purchase #2	$204.74	5.466%	$215.9311	$215.93	$215.95	$215.90
Purchase #3	$212.73	13.529%	$241.5102	$241.51	$241.50	$241.50
Purchase #4	$157.94	4.372%	$164.8451	$164.85	$164.85	$164.80
Purchase #5	$69.31	11.308%	$77.1476	$77.15	$77.15	$77.10
Purchase #6	$123.74	5.865%	$130.9974	$131.00	$131.00	$131.00
Purchase #7	$220.57	6.354%	$234.585	$234.59	$234.60	$234.60
7 purchase totals =	$1,059.95		$1,143.1369	$1,143.15	$1,143.15	$1,143.00