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	$191.67	12.242%	$215.1342	$215.13	$215.15	$215.10
Purchase #2	$49.67	4.408%	$51.8595	$51.86	$51.85	$51.90
Purchase #3	$19.87	10.575%	$21.9713	$21.97	$21.95	$22.00
Purchase #4	$169.39	3.189%	$174.7918	$174.79	$174.80	$174.80
Purchase #5	$76.71	11.193%	$85.2962	$85.30	$85.30	$85.30
Purchase #6	$223.41	12.148%	$250.5498	$250.55	$250.55	$250.50
Purchase #7	$179.81	11.322%	$200.1681	$200.17	$200.15	$200.20
7 purchase totals =	$910.53		$999.7709	$999.77	$999.75	$999.80