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	$59.92	5.838%	$63.4181	$63.42	$63.40	$63.40
Purchase #2	$91.41	11.173%	$101.6232	$101.62	$101.60	$101.60
Purchase #3	$121.72	8.329%	$131.8581	$131.86	$131.85	$131.90
Purchase #4	$189.88	3.399%	$196.334	$196.33	$196.35	$196.30
Purchase #5	$130.80	10.230%	$144.1808	$144.18	$144.20	$144.20
Purchase #6	$76.33	11.613%	$85.1942	$85.19	$85.20	$85.20
Purchase #7	$207.47	9.503%	$227.1859	$227.19	$227.20	$227.20
7 purchase totals =	$877.53		$949.7943	$949.79	$949.80	$949.80