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	$57.27	10.675%	$63.3836	$63.38	$63.40	$63.40
Purchase #2	$205.81	4.689%	$215.4604	$215.46	$215.45	$215.50
Purchase #3	$208.44	9.435%	$228.1063	$228.11	$228.10	$228.10
Purchase #4	$187.87	13.193%	$212.6557	$212.66	$212.65	$212.70
Purchase #5	$84.67	5.734%	$89.525	$89.53	$89.55	$89.50
Purchase #6	$139.53	13.168%	$157.9033	$157.90	$157.90	$157.90
Purchase #7	$228.32	9.269%	$249.483	$249.48	$249.50	$249.50
7 purchase totals =	$1,111.91		$1,216.5173	$1,216.52	$1,216.55	$1,216.60