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	$100.43	11.260%	$111.7384	$111.74	$111.75	$111.70
Purchase #2	$93.94	11.173%	$104.4359	$104.44	$104.45	$104.40
Purchase #3	$82.65	8.798%	$89.9215	$89.92	$89.90	$89.90
Purchase #4	$188.65	7.410%	$202.629	$202.63	$202.65	$202.60
Purchase #5	$164.41	4.240%	$171.381	$171.38	$171.40	$171.40
Purchase #6	$130.63	12.300%	$146.6975	$146.70	$146.70	$146.70
Purchase #7	$107.44	3.631%	$111.3411	$111.34	$111.35	$111.30
7 purchase totals =	$868.15		$938.1444	$938.15	$938.20	$938.00