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	$237.71	7.632%	$255.852	$255.85	$255.85	$255.90
Purchase #2	$89.42	12.683%	$100.7611	$100.76	$100.75	$100.80
Purchase #3	$231.40	9.666%	$253.7671	$253.77	$253.75	$253.80
Purchase #4	$250.67	7.716%	$270.0117	$270.01	$270.00	$270.00
Purchase #5	$17.48	12.334%	$19.636	$19.64	$19.65	$19.60
Purchase #6	$43.34	3.842%	$45.0051	$45.01	$45.00	$45.00
Purchase #7	$7.50	13.874%	$8.5406	$8.54	$8.55	$8.50
7 purchase totals =	$877.52		$953.5736	$953.58	$953.55	$953.60