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	$61.35	6.685%	$65.4512	$65.45	$65.45	$65.50
Purchase #2	$171.74	3.611%	$177.9415	$177.94	$177.95	$177.90
Purchase #3	$189.93	3.443%	$196.4693	$196.47	$196.45	$196.50
Purchase #4	$97.44	3.271%	$100.6273	$100.63	$100.65	$100.60
Purchase #5	$200.74	5.533%	$211.8469	$211.85	$211.85	$211.80
Purchase #6	$182.26	4.513%	$190.4854	$190.49	$190.50	$190.50
Purchase #7	$219.51	11.734%	$245.2673	$245.27	$245.25	$245.30
7 purchase totals =	$1,122.97		$1,188.0889	$1,188.10	$1,188.10	$1,188.10