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	$145.54	7.275%	$156.128	$156.13	$156.15	$156.10
Purchase #2	$176.44	11.558%	$196.8329	$196.83	$196.85	$196.80
Purchase #3	$137.47	13.280%	$155.726	$155.73	$155.75	$155.70
Purchase #4	$237.34	9.559%	$260.0273	$260.03	$260.05	$260.00
Purchase #5	$243.70	5.205%	$256.3846	$256.38	$256.40	$256.40
Purchase #6	$196.62	9.770%	$215.8298	$215.83	$215.85	$215.80
Purchase #7	$94.46	9.763%	$103.6821	$103.68	$103.70	$103.70
7 purchase totals =	$1,231.57		$1,344.6107	$1,344.61	$1,344.75	$1,344.50