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	$103.63	7.333%	$111.2292	$111.23	$111.25	$111.20
Purchase #2	$156.88	11.810%	$175.4075	$175.41	$175.40	$175.40
Purchase #3	$76.82	8.558%	$83.3943	$83.39	$83.40	$83.40
Purchase #4	$156.34	3.470%	$161.765	$161.77	$161.75	$161.80
Purchase #5	$136.57	4.356%	$142.519	$142.52	$142.50	$142.50
Purchase #6	$63.96	10.184%	$70.4737	$70.47	$70.45	$70.50
Purchase #7	$106.79	5.476%	$112.6378	$112.64	$112.65	$112.60
7 purchase totals =	$800.99		$857.4265	$857.43	$857.40	$857.40