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	$41.66	5.390%	$43.9055	$43.91	$43.90	$43.90
Purchase #2	$104.44	6.392%	$111.1158	$111.12	$111.10	$111.10
Purchase #3	$61.81	10.683%	$68.4132	$68.41	$68.40	$68.40
Purchase #4	$225.42	5.852%	$238.6116	$238.61	$238.60	$238.60
Purchase #5	$154.90	12.558%	$174.3523	$174.35	$174.35	$174.40
Purchase #6	$238.41	7.746%	$256.8772	$256.88	$256.90	$256.90
Purchase #7	$149.71	8.706%	$162.7438	$162.74	$162.75	$162.70
7 purchase totals =	$976.35		$1,056.0194	$1,056.02	$1,056.00	$1,056.00