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	$58.26	9.262%	$63.656	$63.66	$63.65	$63.70
Purchase #2	$196.54	6.254%	$208.8316	$208.83	$208.85	$208.80
Purchase #3	$18.82	11.187%	$20.9254	$20.93	$20.95	$20.90
Purchase #4	$107.61	9.272%	$117.5876	$117.59	$117.60	$117.60
Purchase #5	$92.35	13.859%	$105.1488	$105.15	$105.15	$105.10
Purchase #6	$203.42	5.602%	$214.8156	$214.82	$214.80	$214.80
Purchase #7	$99.76	5.110%	$104.8577	$104.86	$104.85	$104.90
7 purchase totals =	$776.76		$835.8227	$835.84	$835.85	$835.80