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	$206.81	4.417%	$215.9448	$215.94	$215.95	$215.90
Purchase #2	$146.77	9.265%	$160.3682	$160.37	$160.35	$160.40
Purchase #3	$158.94	9.866%	$174.621	$174.62	$174.60	$174.60
Purchase #4	$135.51	4.727%	$141.9156	$141.92	$141.90	$141.90
Purchase #5	$67.54	6.401%	$71.8632	$71.86	$71.85	$71.90
Purchase #6	$71.66	8.703%	$77.8966	$77.90	$77.90	$77.90
Purchase #7	$132.85	6.252%	$141.1558	$141.16	$141.15	$141.20
7 purchase totals =	$920.08		$983.7652	$983.77	$983.70	$983.80