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	$17.42	9.874%	$19.1401	$19.14	$19.15	$19.10
Purchase #2	$33.39	9.754%	$36.6469	$36.65	$36.65	$36.60
Purchase #3	$31.83	5.771%	$33.6669	$33.67	$33.65	$33.70
Purchase #4	$78.88	11.301%	$87.7942	$87.79	$87.80	$87.80
Purchase #5	$134.86	10.436%	$148.934	$148.93	$148.95	$148.90
Purchase #6	$205.55	12.448%	$231.1369	$231.14	$231.15	$231.10
Purchase #7	$83.29	7.394%	$89.4485	$89.45	$89.45	$89.40
7 purchase totals =	$585.22		$646.7675	$646.77	$646.80	$646.60