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	$250.79	12.499%	$282.1362	$282.14	$282.15	$282.10
Purchase #2	$51.60	6.784%	$55.1005	$55.10	$55.10	$55.10
Purchase #3	$36.51	12.135%	$40.9405	$40.94	$40.95	$40.90
Purchase #4	$165.29	12.733%	$186.3364	$186.34	$186.35	$186.30
Purchase #5	$153.35	12.488%	$172.5003	$172.50	$172.50	$172.50
Purchase #6	$151.25	10.307%	$166.8393	$166.84	$166.85	$166.80
Purchase #7	$135.69	6.336%	$144.2873	$144.29	$144.30	$144.30
7 purchase totals =	$944.48		$1,048.1405	$1,048.15	$1,048.20	$1,048.00