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	$188.94	5.768%	$199.8381	$199.84	$199.85	$199.80
Purchase #2	$176.67	5.847%	$186.9999	$187.00	$187.00	$187.00
Purchase #3	$25.86	7.256%	$27.7364	$27.74	$27.75	$27.70
Purchase #4	$243.29	5.182%	$255.8973	$255.90	$255.90	$255.90
Purchase #5	$178.67	10.217%	$196.9247	$196.92	$196.90	$196.90
Purchase #6	$176.97	5.800%	$187.2343	$187.23	$187.25	$187.20
Purchase #7	$96.50	6.806%	$103.0678	$103.07	$103.05	$103.10
7 purchase totals =	$1,086.90		$1,157.6985	$1,157.70	$1,157.70	$1,157.60