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	$81.92	5.460%	$86.3928	$86.39	$86.40	$86.40
Purchase #2	$123.26	3.725%	$127.8514	$127.85	$127.85	$127.90
Purchase #3	$86.39	10.269%	$95.2614	$95.26	$95.25	$95.30
Purchase #4	$129.87	7.108%	$139.1012	$139.10	$139.10	$139.10
Purchase #5	$166.33	3.862%	$172.7537	$172.75	$172.75	$172.80
Purchase #6	$232.77	7.355%	$249.8902	$249.89	$249.90	$249.90
Purchase #7	$56.64	3.357%	$58.5414	$58.54	$58.55	$58.50
7 purchase totals =	$877.18		$929.7921	$929.78	$929.80	$929.90