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	$160.98	8.440%	$174.5667	$174.57	$174.55	$174.60
Purchase #2	$16.85	3.361%	$17.4163	$17.42	$17.40	$17.40
Purchase #3	$123.88	8.627%	$134.5671	$134.57	$134.55	$134.60
Purchase #4	$64.98	5.865%	$68.7911	$68.79	$68.80	$68.80
Purchase #5	$206.85	7.597%	$222.5644	$222.56	$222.55	$222.60
Purchase #6	$99.53	12.167%	$111.6398	$111.64	$111.65	$111.60
Purchase #7	$233.45	8.594%	$253.5127	$253.51	$253.50	$253.50
7 purchase totals =	$906.52		$983.0581	$983.06	$983.00	$983.10