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	$101.43	9.515%	$111.0811	$111.08	$111.10	$111.10
Purchase #2	$220.38	10.529%	$243.5838	$243.58	$243.60	$243.60
Purchase #3	$182.92	11.556%	$204.0582	$204.06	$204.05	$204.10
Purchase #4	$43.73	4.793%	$45.826	$45.83	$45.85	$45.80
Purchase #5	$138.70	8.443%	$150.4104	$150.41	$150.40	$150.40
Purchase #6	$111.65	4.698%	$116.8953	$116.90	$116.90	$116.90
Purchase #7	$151.62	13.469%	$172.0417	$172.04	$172.05	$172.00
7 purchase totals =	$950.43		$1,043.8965	$1,043.90	$1,043.95	$1,043.90