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	$236.88	9.696%	$259.8479	$259.85	$259.85	$259.80
Purchase #2	$122.44	4.176%	$127.5531	$127.55	$127.55	$127.60
Purchase #3	$100.28	5.271%	$105.5658	$105.57	$105.55	$105.60
Purchase #4	$58.64	12.693%	$66.0832	$66.08	$66.10	$66.10
Purchase #5	$202.78	3.779%	$210.4431	$210.44	$210.45	$210.40
Purchase #6	$137.63	5.275%	$144.89	$144.89	$144.90	$144.90
Purchase #7	$236.93	5.503%	$249.9683	$249.97	$249.95	$250.00
7 purchase totals =	$1,095.58		$1,164.3514	$1,164.35	$1,164.35	$1,164.40